Ralackk: The bots in Chivalry are unfortnatly brain dead and pretty useless. I was able to play an archer and stand a good 5 feet away from one of the enemys and turn him into a pin cushion and he didn't even move, just stood there. I also noticed they all tend to get stuck on the terrain alot so you also get pile ups of them milling about not doing anything.
carnival73: Bugger, that confirms it. Chivalry's longevity is only as good as the duration of its popularity.
Well, Age of Chivalry, the HL2 mod it grew out of had a fairly active player base in the hundreds until the updates dried up.
Warband is nearing two years old and updates for the base game are very infrequent/dead, though it remains extremely popular. However, the game is HEAVILY modifiable and has a single player campaign. Also, had a recent DLC release.
Another HL2 mod, Zombie Panic! Source remains somewhat popular, although it still gets the occasional update. It's probably more than five years old and I'd imagine closer to seven.
Game life is very hard to predict, but if the game is good it will live on. Myth 2 hasn't been purchasable in over ten years, but there's still consistently 30 hanging out in games or lobbies on MariusNet.
Really, the only games multiplayer I'd worry about are those that rely on Gamespy.