Battery life cut after 3.1.3 update on iPhone 3G

I have the same issue since I upgraded my iphone to 3.1.3.
I also have a problem with the wifi signal. It is not able to find anyone.
Any idea to back to 3.1.2?
Iphone 3G iPhone OS 3.1.3

I havent updated yet but IIRC the updated says it improves battery level accuracy. Maybe you need to let the iPhone measure your battery charge again. To do this completly drain the battery till the phone shuts itself down. Then do a full charge. Then use the phone till its completly drained again & do another full charge. Hopefully this will reset the battery charge measurements.
imac, iPhone 3Gs

Since updating to 3.1.3 my battery life has been better.
Lenovo T-60, Intel iMac , Dell/Ubuntu 8, iPhone 3GS 3.1.3 Windows XP Pro Leopard 10.5.4

mine too!
imac Mac OS X (10.5.6)

I am also having problems with battery life since upgrading my iPhone 3G from 3.1.2 to 3.1.3. I had no problem going a whole day with quite heavy usage on one charge before, however since updating the firmware it only lasts about 5 hours with NO use. My battery fully discharged last night and was fully charged this morning, but dont want to have to spend my evenings without a phone so need to charge it mid-day... not happy at all!
iPhone 3G iPhone OS 3.1.3