Quote Originally Posted by Hornypony View Post
Later girls have more diamonds and less energy and I think after Twins only diamonds. If I have not forgotten a purchase of a 20 energy block, free energy will end at 102 somehwere within Zoe or Twins.

That would be 3-4 slots per girl after Pantress.
Confirming the 102 figure; I'm just finishing Twins for the first time and I'm on 101 (with 1 more to earn once this filming finishes).