[PPCGeeks4ME]

I'm now getting 40 hours of light use with GPS and WiFi on. Granted this is with a custom ROM and kernel undervolted for battery life.

When you say your WiFi is on, are you actually connected to a WiFi network? That's a major battery saver as the WiFi radio uses less power than the 3G radio.

As for GPS, it seems to me that the GPS doesn't actually turn on until a program needs it. The switch is more like a permission check, so you can make sure some app isn't tracking your location without your knowledge. I don't think it hurts battery to leave it on, but I don't think it helps battery either.

When I turn BT on, it uses about 25% of my battery according to the battery life screen, even if I'm not using it. I'm going to try turning it on again tomorrow to see what its real effects are.