i can remember reading in another thread that, because squall's level determines the monsters level, you could leave squall dead the whole time, so that he does not level, and this will stop the monsters levelling up. then you can just level up 2 characters and own all the monsters . . .
however . . . i never found out whether this would actually work. i think someone said they'd try it but i never looked it up again. so can anyone tell me whether this works or not?