Really, as a general rule, MUSHes give out too much XP, and characters advance too fast.
The first is more or less a function of the 24/7 availability of a game, combined with how many games want to reward activity. I mean, if you used the suggested XP per game and then ran your tabletop game 7 days a week, XP would inflate pretty far pretty fast as well.
The second you just have to sort of suck up and deal with, but has its roots in similar issues. In a TT game the ST can sit you down at the table and say "Okay, it's been six months since you X'd the Y of Z's plans to A the B, and you've all kept in touch." or whatever else describes lends to a sense of the passage of time and gives the advancement of abilities a sense of scope.
I don't really know that much can be done about either. People do like to see their characters advance, and at more than a snail's pace, and there's no denying that XP for activity/participation serves to motivate people to participate more. As with anything, that can be taken to an unhealthy extreme, but it's true enough even for people who aren't trying to abuse the +vote/PRP system for xp.