If your phone is ZiPhone’d or Pwnd recently to firmware version 1.1.4 , you must have noticed a considerable decrease in the battery life. Here are some working fixes:-

Phone settings;
Brightness: [-o------] Keep to the minimum. 
Auto Brightness: on
Ask to join networks: off
WiFi: Keep it turned off all time. Turn it on only when needed.
Mail send & receive: once a day

Upgrading your bootloader from 3.9 to 4.6 also improves the battery life. You need the BootNeuter iPhone application(Installer Source: http://scape-server.org/iphone) and run it with the following settings. Make sure that you have set the [set auto lock to Never in iPhone settings screen before doing this]

After flashing is successfully over, reboot. Your iPhone will have more battery life now.

Tags: battery life, bootneuter, iphone