Originally Posted by joblack
12 hours? Never - I've got an iLiad V2 and using FBReader. The maximum is 8 hours. If you use an USB Stick even less (USB sticks are leeching power like hell).
Using memory cards/sticks, the pen, etc, will all drain the battery faster. If you do nothing but read and turn pages it should give you around 15 hours with a V2. If you're significantly short of that, you might have a battery problem. You can try contacting their support and see if they'll replace it under warranty.
On my V1, I get slightly more than 12 hours just reading.