I read a lot on my iPad, and now 7+ too since it has a big enough screen. For hours at stretch. And like other people paranoid about battery life I keep an eye on the battery percentage too. One thing I noticed that when at home, the phone battery drains 1% every 13-14 minutes while I'm reading using Play Books. Now when I'm trying to get my mind off something I walk in my room. So yesterday I was reading while walking in circles in my room. Now the battery was draining every 10-11 minutes. I turned off Auto Brightness first and then put it onto Airplane mode to minimize those factors. The difference was still 3-4 minutes. I tested this 10 times (and finished half a book). Nothing explains this behavior. The battery draining won't be apparent when you use your phone heavily but factors in tasks like reading and listening to music. Motion and Fitness are integral features for me but isn't the M10 coprocessor supposed to save battery life?