it's hard to determine because I think their self confidence should be considered too. if you log in daily you can check it regularly. when no more boost or maybe small from clothes then we must change.
http://www.mmatycoon.com/fighterprofilemanager.php?FID=274500 100% with 112
http://www.mmatycoon.com/fighterprofilemanager.php?FID=221675 94.35% with 130 and won't change until his bout