With my iPad 4 (64 Gig wifi + AT&T 3G) I normally get close to the advertised ten hours of battery life with a full charge, whether I am browsing or playing games. However, if I read on the Kindle app, or the iBooks app, or the Nook app, or the Kobo app, my battery drains like crazy. If I only read, I would not get more than four hours and forty minutes of battery life with a full charge! I have auto brightness on and the brightness set to full. Is this normal, or is something wrong with my iPad?