What I do is turn off 4G and 3G ALL TOGETHER when I'm not using the phone.
It extends battery life by at least 2 to 3 hours.
You can turn off 4G by swiping the notification bar down -- you will see a button for toggling 4G. You can also turn off 3G by going to Settings --> More... under Wireless and Network --> Mobile Networks --> 3G Data.
There's also a widget app that lets you bypass the stupid settings / notification bar, and let you toggle data by just tapping on the widget.
Here's the link. I think this is the only one that works on Epic Touch.