that sounds ridiculous..where did you get your batteries from?
All eGO batteries are fully charged within two hours at the most. Your 900mAH will last you nine hours when fully charged. After you charge one, charge the other so you have a back up. You don't want to charge your battery for eight hours..any battery for eight hours..this will wear and tear your battery.
I fried one of mine when I forgot about it five hours later.
Vape for twenty minutes? Please, no..that's just silly.
I am a total eGO fanatic..When the light turns green..it is done unless you get a bogus charger.
The minimum time for an eGO is like an hour, but it wont last as long. I can send you some instructions on how to maintain and keep well if you'd like.
Edit: With every eGO I have bought, built or refurbished..I have never seen instructions like that. On all of my new batteries, first charge, they worked perfectly about two and a half hours later. I've never charged mine for that long..Although, even if it says that..my common sense says no. That's just me though. Experience your own