My battery was pretty good until the last 2 weeks where it was dying every 4-6 hours. I thought it was an array of apps (Spotify, Skype, Nokia Maps) and I uninstalled all of them and the battery didn't improve. I decided to do a factory reset and, after fixing the bricked phone, I was able to get my battery life in excellent conditions. Battery now last between 1.5-2 days compared to the previous 6 hours.
I strongly suggest if you are having any issues with the battery, try multiple soft resets, if that doesn't work, backup your data and do a factory reset. Beware do, your phone could brick during the process and you might need to un-brick it. I used the WP guide Tip: How to fix a bricked Nokia Lumia 920 | Windows Phone Central and it worked flawlessly.
I strongly suggest if you are having any issues with the battery, try multiple soft resets, if that doesn't work, backup your data and do a factory reset. Beware do, your phone could brick during the process and you might need to un-brick it. I used the WP guide Tip: How to fix a bricked Nokia Lumia 920 | Windows Phone Central and it worked flawlessly.