Auto Brightness
I don't think this is an auto brightness issue because I'm always on default settings and I've been using my iPad for a month, and I have no complains about the battery life.
Have you tried closing the apps that you are not using? closing them from the multitask bar, that's what I always do... I just keep the Facebook, Twitter and Safari apps for quick loading.
another tips...
- Don't you ever! place the iPad on top of hot places, like your PC monitor
- Set auto lock screen to 1 minute
- Turn off equalizer on music
- Once a month, drain the battery and do a full charge