...I just reached the Monastery in the first chapter of the game, and I'm 78th level.
At first I was going up 4, 5, 8 levels at a time--get into combat, hear the "level up" sound several times before the combat's over--but now that I'm farther along, and much higher level, it's slowed down considerably.
But 78 levels is as high as I got my prior experiment, the character without the EP bonus charm.
...so I think I may finally get a character to 99 levels before finishing "hell" mode. That would be nice.