Terrible iPod Touch 4G Battery Life

I have an iPod Touch 4G. It's about 1 year old, and in great condition, except the battery life. The batery life is unbearible. I watched the battery icon on the status bar drain slowly to 20% and getting the low battery alert. I've done everything I can possibly think of. I've turned optimized all settings(Bluetooth off, WiFi off when not using, Mail set to manual, minimal notifactions), closed every app except the one I'm using out of the background, restored in iTunes to factory defaults, but nothing's working. I have no idea what to do. This actually happend about 2 years ago when I got my first iPod Touch 4G. It was the same exact kind as the one I currently have, and it had the same problem. I took it in to Apple repair, and since my warrenty was just almost up, they replaced it. It helped for about 2 months, and then I have the same problem. I finally posted here because I've run out of options, and it's even worse than my old iPod Touch was. Any help would be awesome. There's no way I'm getting it replaced for $79, and I would like to resort from finding a cheap iPhone 4 on eBay. Thanks!