The “standard” model of the neverending campaign is a lot less standard these days — it’s enviable, but gets harder and harder to pull off the older you get. Multiply moving, having kids and other responsibilities by the number of players in your group, and it quickly gets tough to keep a game running for that long.
There are groups out there doing it, though (including at least a couple of TT members I can think of), but more and more often lately I see, hear about and participate in shorter-term campaigns.
Personally, the longest campaign I’ve ever GMed lasted somewhere between three and four years (1989 to 1991 or ’92, which is why I’m a bit fuzzy on the details). How about you?