This is the problem with everyone just telling people to turn off wifi or 3G to save battery. It doesn't spread any knowledge, only actions. Weak/no signals drain the battery more than anything you could do with your phone, more than 3D games, more than recording 720p video. If you are using wifi with a strong signal, then 3G won't even be in use (no need to disable it).
Strong signals = good battery life. Weak/no signals = bad battery life. Sure, you can turn off all the radios and have good battery life, but you certainly don't need to. Of the radios, 4G drains the battery the most, then GPS, then 3G, then wifi. If you can, use whatever has a strong signal for best battery life. Turn off the radios when you know there isn't a good signal.