Bonus Levels/Donuts

I'm sure there are threads from a few weeks ago that give the numbers, but I believe that at level 100 it changes to 500,000 XP (could be wrong about this number) and then once you hit level 939 it's 1,000,000 XP for bonut boxes. Level 939 is the max right now.

And yes, you should definitely be grinding for donuts.