I had an issue with my T-Mobile M9 draining 30% of power in 6-7 hours (when I was asleep) with all apps closed and the phone restarted. I got fed up with the power drain and factory reset the phone. Since that factory reset, the battery life has been amazing. I now lose about 3% of power in that time frame. I also noticed after the factory reset, the home screen locked changed. Not sure why that is as I had updated my phone's apps fully prior to factory resetting. Factory resetting is probably not what you want to hear, but it worked for me.