This game has broken me. After reading the other comment that says the max lv is 71, I've been grinding xp in the final area to see how far I can push it.
I'm now level 19.
I'm posting this because I need you to know that, I, a 20 year old woman, have just spent close to 4 hours playing this game.
The only negative thing I can say is that after roughly level 15/16, Shimmer's bust shrinks when you hit max milk capacity.