By about level 30, depending on your team, any further levelling is kind of moot. This is highlighted by the fact that beyond this level, all subsequent level ups only offer small stat/HP bonuses, and take the same amount of experience. However Hit%, the factor that increases the number of hits, will continue to increase linearly. Also Mages will generally gain more MP at higher levels (however they will max out their lower level MPs earlier, meaning they technically gain less at higher levels). I personally have finished the game with a Level 35~ party.