Goal keepers typically go on for an extra season or two in X11, but the principal still applys, that the older they are. The more chance they'll retire on you there is, and it doesn't matter how skilled the player is, or how high his form is. It's a random counter thing. That's why I wouldn't bid for over 30 players near the end of the season, they could just play a few games then say bye. Hell, players in their 20's can ertire, the chances of it are just an awful lot lower than players in their 30's, and every year older the player is, the higher the chance he'll retire until it get's to about 36 where it's a 50/50 from there onwards.