In most games you will find guilds targeted for the older gamer. Usually their requirements will be 30+ or sometimes 25+. I was once in one of those guilds but found my play style didn't quite fit in with the guild. I was older than everyone else but at the time just attributed my differences more towards me in general than my age.
While our guild in EQ2 doesn't have an age restriction, we advertise ourselves as most members being 30+. But actually we've evolved into a 40-60's guild. As we've grown, I've noticed that there tend to be certain differences in the 30's crowd compared to 40+.
When a new member joins and they tell me they have a Ventrilo server we can all use, in all cases it turned out they are in the 20's-30's. The first couple times I received the offer, I asked in guild chat. But there was absolutely no interest in it, so I've gotten in the habit of declining up front. I can't speak for the other members' reasons, but I know I have no interest in hearing voices while I"m playing. I actually like the ambient music in games and would much rather hear that. EQ2 will be implementing their own voice chat which is currently on test server, so we'll see if this changes anything for us.
When a new member joins and asks how they move up in rank in the guild, in all cases they were in their 20's-30's and male. I specifically set up the guild to give little weight to rankings. I turned off promotion announcements so guild members don't see when a promotion occurs. Having a higher rank doesn't make one better or more valued so I place no emphasis on it.
Something I've noticed specific to the older female is a strong dislike for PvP. There are a number of couples within the guild, and while the husbands were very open to PvP, the wives wanted no part of it. As I said, this applied only to the older female player. We have several under 40 couples and in most all those cases, the wives did participate and some even enjoyed PvP.
The older females tend to be more social and community driven. While the game may not be perfect for them, they are more likely to stick around because they like the people around them. And often they are the driving force behind which game the couple is playing, so the husband is there by default.
Keep in mind these are my observations in EQ2. Older gamers in another MMO may very well have different tendencies. But what is it that happens somewhere around 40 that changes gaming perspective? We are not all gaming vets from EQ1. Some played WoW as their first MMO and for some EQ2 is their first gaming experience. So it has nothing to do with number of years played.
Maybe after so many years of working, dealing with teenagers, or going through life in general, we're seeking less structure and more camaraderie? I honestly don't know why that dividing line occurs, but I do know the 20-30's tend to eventually move on, while our 40-60 bracket grows. Will be interesting to see how MMO's evolve in 20 years to accommodate the interests of the aging player base.