I've been using Android devices for a little over a year now. As most Android users find, battery life ain't great.
There are a plethora of apps out there that claim to extend battery life and, believe me, I've tried a few. In most cases, I've found they actually increase battery drain, or render the phone almost useless by shutting down all those wonderful things we wanted it for in the first place.
So, here's my tip which will let you use your phone pretty much whenever you want without having to worry about the battery draining empty. Buy yourself a charger. Or maybe even two. Keep one at work and plug it in whenever you're sat at your desk. Buy a car charger so it's charging all the time you're on the road. Given that you get a charger with your device, you can leave that one at home.
My two chargers cost me about 20 quid from Amazon. That's less than I've spent on various battery-oriented Apps over the past year and is a better solution in every possible way. Who cares if it's tethered whilst it's charging if you're sat next to the thing anyway?
Save yourself some cash and get a charger for every location you're likely to be in. I've even got one I carry around with me "just in case" - it's so tiny, I barely notice it.