Amazon states 8 weeks, when reading half an hour per day with the light on 10 and all data connections off.
If you read 2 hours per day, battery life drops to 2 weeks (25-30 hours). Should you set the light higher than 10, battery life will become shorter still. Some people also leave wifi (and 3g) on for syncing.
Last edited by Katsunami; 02-02-2013 at 11:58 AM.