This is getting off topic, but I prefer to use XP (and XP analogues) as advancement markers, not as incentives. I tend to do "fiat" leveling--you level up when I say you do. I'm planning to move to a session-based approach--each session that the party does something meaningful (as decided by them), they get a mark. A certain number of marks (starting small and growing to a cap) gets you a level. The only incentive here is not to totally waste your and everyone else's time. I don't care what you do (not marking story beats or kills or anything), just that you're engaging with the world and the characters. I've had meaningful sessions where they spent the time playing with goblin children, helping a goblin tribe gather food, and otherwise "sitting around". We may have made a total of 1 check that whole time. But it was one of the better sessions as far as players' attitudes.