A problem I have in a classic dungeon exercise is that really the players could simply back off and heal often at any time (generally nothing in the game world (atleast as I envision it) naturally stops this - only if I force an event to stop it from occuring, can it be stopped)
However after playing dragons crown, they have a mechanic where every dungeon you do after the first has an increase in gold and XP gained. If you were to go back, this resets back to the default.
I'm really liking this. In the past I've considered having enemies remove treasure from the dungeon if the players withdraw. But that's kind of missing out on something - don't gain for being bold, you just miss out if you are not bold. Of course the opposite is quite simple - have it possible to gain more treasure. Of course a bit of a simulationist attitude blocks this idea from being cognised. Because why would more money appear? But having played it, I know it's fun! So the reason more money would appear is that its fun (it's a particular type of fun and delivers it nicely).