Cumulative power ups? Mostly haven't gotten one yet. My epic win is so big that there really aren't any intermediate steps, or not many that won't take weeks worth of effort. Feels sort of like I've "failed" when day after day I don't do any of my quests, just lots of powerups?
(I am a player, not an in charge person.) Have you tried breaking your "weeks worth of effort" quests into smaller bits? Shorten time spaces, break actions down into bite sizes, shorten counts, etc. it's hard to provide relevant examples without knowing what the epic win is, nor types of quests you have written. I don't know how to contact you, but if you know how to contact me, please do. I'm willing to help you figure this out.