Honestly, it depends on the ski. Most skis can handle 3, some can handle only 2, there are even a few that can only handle 1...there are also skis out there that can take like 4 or 5 mounts (but you have to change the way you ski them...these are usually thick core, wide, hard charging powder/big mountain skis...but after 2 or 3 mounts they really become an all-mountain/cruiser ski).
What skis are you looking to remount...then you can get the best answer possible.