I can get about 2 days out of 1 full charge. There are just a little tweaks to your setup and I have jailbroken.
3G signal not optimal - usually same
brightness 80% - usually same
Location services & push notifications on - push on for SOME apps! Location is off unless im using it. Which is rare(me using it).
Wifi on but no hot spots available - again unless im connected to wifi its off!
Bluetooth off - never use it as its useless on iphone without headset.