Last Bible trilogy observations

In Last Bible III, beast levels are capped at (base level + 4). That is, they can only gain four levels on top of whatever they start with when you first recruit them. They simply don't gain any more EXP afterwards, and the EXP to next level displays 0/0. If you're trying to level grind, and you're not relying on them to help you win battles, you should probably shelve maxed-out beasts until you actually need them.

Official team members (humans, the dragon, Harry and Du) have no such restrictions. You can level them as much as you want. 

Last Bible 1 and 2 cap character stats at 40, though they can still be increased further through use of stat-raising charms. Last Bible 3 caps character stats at 50. If you put points in a stat that's already capped, it will have no further effect, so watch out!