Well, uhh... The fandom actually did exist about twenty years ago. It has it's beginnings somewhere in the early 80s, if I remember the furry historians correctly. The fandom wasn't terribly accessible back then, of course. The organised aspects of it mostly began out of room parties in cons in southern California. Furry is just a heck of a lot easier to find, these days. It's more approachable than it had been, seeing as it's very openly spread all over the internet. You used to have to know exactly where to look, back in the day.
Some of the earliest long distance text based communications consisted of dial-up BBSs each with their own local discussion boards and then a long list of "echoes" which were shared from BBS to BBS in an automated "slow mo" internet sorta fashion that required the BBSes to dial long distance to each other in the network and update each other on what had been posted to the echoes' threads. I was on one of these back in the mid 90s, called The Trap Line, based out of Toronto, Ontario, Canada.
You may notice that the youth are what drive a lot of the discussions, noisy parties, flamboyant furryness, and whatnot... however, it's typically the greymuzzles that do things like run the web servers, run MUCKs, build community services and tools, administrate conferences, and whatnot. Yeah, there're some younger furries that run their own services along these lines, but the most established services are by greymuzzles. Maybe those greymuzzles were particularly young when they started these services, but they've withstood the test of time and have well-established services now. Greymuzzles are the quiet backbone of the community.
Longevity isn't a very common thing in this fandom, I find. A lot of furs join as they're young, then either RL distracts them off to other things, they grow disinterested, or whatever. Greymuzzles are becoming more populous for the simple fact that the fandom started to see it's first big influx of young fans about ten to fifteen years ago... and those that have survived since that time are now into their 30s and so on.
I dunno if it's so much a "young person fandom" as it's a "young person world" in general. In society as a whole, youth tends to dominate culture, as a driving force behind what is considered fashionable. Furry always seems to echo mainstream culture in some way or another. It's in our nature in general, after all.
Where I live now, I am perhaps the oldest of the furries... and I'm just 34. There're a bunch of us around our early 30s in age, then there's a bunch that are in their college years. We all get along fairly well, at least. I seem to have a fair bit of respect from the younger furs... but some of that may be from the fact that I run furry.ca and whatnot.
Benjamin