It has nothing to do with factory reset, or hard reset. I started out with great battery performance, only to see it get worse. Reading the posts I finally decided to try the menu driven factory reset. Well, what do you know, it worked, for a day or two. Well, there is really nothing logical about a reset helping the battery. So after a week of having bad battery life i did the following as an experiment. I charged the battery fully. Then I cycled power off, (similar to a typical reset) and cycled power back on. Well, what do you know, battery life is much better. I think what basically happens is if you leave you phone on for day on in, over time, with the many apps running, etc, even will all the task killers, etc there are residual background tasks that suck battery life. A power cycle is the ultimate task killer. Anyway, my example. On Thur, phone off the charger at 7am, by noon I was at 60%, by the early pm i was at 30%, etc. Today, after the power cycle, phone is off charger at 7am, its now almost 10pm and I am at 50%, about the same usage. So, periodically, after a full charge, cycle power.