Adults that live past age fourty are considered venerable and accorded a great deal of respect.
Life and Death
It is interesting to note that Mandalorians live very full lives but at the same time accept death as a natural and inevitable part of life. Most Mando'ade do not go to excessive lengths to prolong their lives and are not obsessed with immortality the same way most cultures are. While they try to avoid death by becoming masters of their environments and superior soldiers, they don't avoid dangerous work or limit their life experiences in fear of it.
The Mando'ade believe that there are far worse thangs than death and dying. The old army addage "death before dishonor" is an apt descriptive of how Mandalorians view life and death. This is a people who prefer to live useful, vibrant and inspiring lives over longer, less satisfying and noteworthy ones. In other words, while a Mandalorian isn't going to go chasing an untimely death, but is likely to stand and fight if death comes chasing him.
The daily custom of aay'han ("remembering and celebrating") in which they take time to remember those close to them who have died explains a great deal about the Mandalorian view of death. It is both a way to honor those who have passed and give them a form of immortality by keeping their spirit and memory in their daily lives. Paired with the commony held belief in an afterlife in which the passed enjoy an eternal life with their families, losing one's soul by becoming dar'Manda seems far more frightening than mere physical death by comparison.
An example of the Mandalorian mindset on the dead is their treatment of their dead. It reflects their practical nature and attitude. Whenever possible, survivors will return the beskar'gam (armor) of a fallen Mandalorian to that person's family, who will parcel plates out to be worn by the survivors. Only in very rare instances will a body be returned to the surviving family for burial. Formal burials seem to be reserved for Mand'alors, who are (when possible) returned to Mandalore and buried. During wartime, mass graves are favored, as is noted in Traviss' novel "Sacrifice".
Word As Action
A Mandalorian's word is a declaration of his intent and can generally be relied on. This is reflected in the seemingly informal nature of their social contracts with one another. Rather than drawing up wordy, documented contracts with each other, they opt for simple, brief exchanges.
Adoption is literally a single sentance between a Mandalorian and his intended child. Ni kyr'tayl gai sa'ad. (I know your name as my child.)
Marriage is a mere set of four short lines, spoken together.
Mhi solus tome. We are one together.
Mhi solus dhar'tome. We are one when parted.
Mhi me'dinui an. We share all.
Mhi ba'juri verde. We will raise warriors.
Divorce or disownment is literally only a terse statement that declares that the divorced party is no longer known.
Pacts are sealed with a mere three words. Haat, ijaa, haa'it. (Truth, honor, vision.)
It is easy to look at this contractual simplicity and get the mistaken idea that Mandalorians are primitive and naive. This would be a very unfortunate assumption to make. When dealing with outsiders, they are shrewd and canny bargainers, often intimately aware of galactic law and business and using this knowledge to create advantageous and ironclad contracts with their business partners and clients. They look down on cumbersome bureaucracy with contempt, but will never hesitate to exploit it if and when situations neccessitate it in their dealings with outsiders.
More Than War
The Mandalorians have two central focuses that their culture revolves around: war and family. I've seen a lot of folks with this mistaken idea that the Mando'ade would find simple things like farming or herding to be beneath them. Nothing could be farther from the truth. It is established EU cannon that the Mandalorians, while not at war, are successful farmers, talented craftsmen, skilled doctors and so on.
In some of Karen Traviss' EU work, the Mand'alore is rebuked by some of his people and reminded that harvests have to be gathered and homesteads tended when he meets with representatives of the aliitse to discuss a considered contract which he plans to call them to take part in. There are mentions throughout EU cannon about peacetime occupation, familial concerns and financial management. This all points very firmly toward a society that while it centers on war does not pursue it exclusively to the detriment of other responsibilities and pastimes. In short, while every Mandalorian is a warrior at heart, they are also farmers, artisans, scientists and laborers.
This is only common sense, as a society entirely made up of soldiers, lacking the skill or desire to include other needed occupations cannot exist for long without a very large number of slaves, which cannon suggests that the Mandalorians do not have.
Mandalorian Honor
Mandalorian honor is a very tricky thing that may be the most widely misinterpreted and mis-played facet of Mando'ade culture. This is unfortunate, as it is a huge part of convincingly playing a Mando'ad and ties into nearly every part of their culture on one level or another. People naturally cast their own interpretations on the definition of the word "honor", ignoring all expamles of what it is meant to be from EU sources. Mandalorian honor is not (and does not even resemble) modern society's active pursuit of pride. In fact, behaving in character as most would in real life in situations where one's pride is an active factor is often dishonorable and even repugnant in the context of maintaining honor as a Mandalorian.
It is illustrated throughout EU cannon that Mandalorians that are respected among their people are as a rule quiet, respectful (where respect has been earned), responsible and deeply mindful of their actions. They aren't prone to being loudmouthed and braggarts, and don't tend to have any respect at all for those who are. They give warnings rather than make threats, as they seldom need to resort to that kind of thing, even when dealing with outsiders. Their strict adherence to their cultural sense of honor has created a perception that makes it unneccessary.
Honor is gained through being intelligent, skillful, productive and dependable both on and off the field of battle, both in combat and out of it. An often quoted saying about Mandalorians that illustrates this is "there is no word for hero". Honor is not reserved to enhance a single person's status, but enhances and gives glory to an individual's family and clan, and to the Mandalorians as a people. Where we, as members of modern society feel a sense of personal strength and wellbeing for and of only ourselves, in Mandalorian society, this is a shared thing, tied strongly into the concept of Manda and reserved for aliitse rather than individuals. There is more at stake in how a person behaves than mere personal pride and entitlement, because every person's actions add to or detract from the honor and standing of their aliit.
Because a great number of Mando'ad Verde are mercenaries or bounty hunters, people tend to have misconceptions about what is considered honorable when it comes to fighting. Canon tells us that the Mandalorians were among the most ferocious and feared soldiers in the galaxy, and EU history is filled with wars and battles in which the Mando'ade were directly involved. Their history is one of conquest, from their origins as the Taung to their involvement in the Clone Wars. Naturally people assume that this means that they are generic killing machines wearing really cool armor who'd shoot your granny if they were paid enough or if she waved her cane at them. This is, from what I understand, definately not the case.
Instead, we are looking at and trying to portray people who find it abhorrent to kill a person who is not a threat to themselves or families or who is not able to defend themselves under most circumstances. Doing this kind of thing without some extremely valid extenuating circumstances is viewed as cowardly. Cowards are viewed as the lowest of the low in Mandalorian culture. Cowardly acts disgrace those who do them and the families that they are part of equally.
This brings interesting ethical quandries to the table in roleplaying a Mandalorian, sometimes presenting obstacles to overcome that other, aruetii players don't face. It makes being Mando'ad a challenging prospect for most players, because they aren't able to make the connection between certain acts and cowardice as percieved by the standards of the culture in which they are trying to play a role.
Here is a good example of Mandalorian honor at work.
A Mandalorian soldier is drinking at a bar, enjoying some downtime after a hard job. An obnoxious drunk (seeming to be unarmed, wearing no armor), obviously cruising for a fight starts talking trash. The Mandalorian ignores him, even when the man calls him a coward (the worst insult a person could give a Mandalorian).
The Mandalorian in this example is being honorable. The drunk presents no actual threat and is in no condition to do any real harm to anyone but himself and his own reputation. If the Mandalorian had risen to the bait of the insult of being a coward, and attacked the drunk, he would have indeed deserved the insult. The Mandalorian is secure, knowing he is more than capable of hurting or killing the drunk if it became absolutely neccessary to do so.
Had the drunk pulled a weapon or attacked the Mandalorian, it would have been not merely honorable, but neccessary to defend himself, dealing with the threat as expediently as possible with as little fuss as possible. Killing the man would not be the first impulse, as there would still be no honor and a risk of staining the aliit's honor with a cowardly act.
Now before you get the idea that Mandalorians might be peaceful carebears because they think killing someone defenseless is cowardly, let's look at who it's a-ok to put out of the galaxy's misery -- namely any foe who is either threatening a Mandalorian, his family, his clan or his people and anyone who actually knows which end of a blaster or blade to hold and happens to have access to one...most especially folks who are really good at that.
The harder the opponent, the more honor is to be gained in defeating that opponent. The more difficult and dangerous targets you take down, the higher that level of respect and honor becomes. But it needs to be noted that the Mandalorian who is careless or takes too many outrageous chances without having to is not looked at as honorable, but merely suicidal or stupid instead. So yet again we see a balancing act going on in honor.
And it gets even more complicated. Because your track record isn't just measured in who you kill or defeat and who you don't. It's also measured in how you do it and how you win or lose. And this is one of those places where a lot of people screw up in roleplaying a decent Mandalorian. Because they forget that "how you play the game" is just as important as the body count.
Unless your foe has done something exceedingly dishonorable, you are expected to face them with a certain measure of respect. This doesn't mean a Mandalorian is going to hold back or not resort to every trick he knows to take a foe down -- that would be like saying that foe wasn't worth fighting. What it means is that unless there's a really good reason, a Mandalorian isn't going to do something disgusting like descecrate a corpse, rape their fallen enemy's women and children, or anything along those lines. In point of fact, a fallen enemy's children may just end up becoming part of the Mandalorian's family if they show enough guts and spirit.
And should a Mandalorian end up losing a fight or battle, it's not considered honorable to make excuses, badmouth the winner or carry unearned grudges over the loss. To the contrary. It is honorable to seek to learn from the winners and occasionally, if the winners are honorable and a great deal more skilled and powerful, to take service under them for a time.