I own an iPhone 3GS and generally only get about 5 hours of usage with it starting at 100% at the beginning of the day. I keep bluetooth and notifications turned off. Brightness is set on Auto and at about 50%. I rarely ever use GPS. Mainly just internet and texting, with possibly one or two short calls a day. I use WiFi a good bit of the time and 3G when I have to. I feel like I should get much better battery life. I also constantly close any apps that could run in the background.