[HTCotta]

I only turn it on when I need it, but i haven't personally run any tests to see how big of a difference it makes. The less radios that are on, the longer your battery will last. If you have 3G, 4G, wifi, bluetooth, and gps all on, battery will die fast. Turn some off while not in use and you will notice a big difference. I recommend using the program widgetsoid to put toggles in the notification tray so you can easily turn everything on and off without going back to your homescreen.