Originally Posted by RevShare it!

I have found out when i'm usually low in battery and out and about and can't afford for my battery to die I can go for quite a while with 3G turned off.

Turn off 3G: Using 3G cellular networks loads data faster, but may also decrease battery life, especially in areas with limited 3G coverage. To disable 3G, from the Home screen choose Settings > General > Network and set Enable 3G to Off. You will still be able to make and receive calls and access cellular data networks via EDGE or GPRS where available.

Also WiFi & Bluetooth drain it