In my league, we just have a player add limit as others suggested here. Also set is a weekly IP minimum. Also, we have special playoff rules on player adds so no one saves all their moves for the playoffs. We're still tweaking the playoff restrictions, so I can't say exactly what we do there just yet.
Unfortunately, Yahoo doesn't allow a weekly innings maximum, or else I would seriously consider that. That's the case in their free game, anyways. I'm too poor for the pay leagues.