The problem with the battery app always has been that it uses more power checking to see if it's needed to be turned on than it saves once it is actually on. Most users regularly won't let the battery get so low as to need the app anyway. Turning it off saves a lot more drain on the battery than it should. Since I am on T-Mobile, I still don't know how 8.1 will affect the situation, but with 8.0 I can usually get near two days before I need to charge it with moderate Internet use, about an hour, and a few phone calls.