I'm always leary of manufactures claims of battery life, my rule of thumb is to cut what the manufacturer says in half.
Many users have been complaining of significantly lower battery runtimes with the touch. Here's an example:
I purchased an iPod Touch (16 gig) last week. I have been waiting for iPhone service in my area, but waiting is painful.I am really disappointed with the battery life and standard features of the iPod Touch. Battery life is totally unacceptable. After 3 to 4 hours of listening to podcasts I got the warning that 20% of the battery remained.
After a fully recharge I attempted to play a 2 hour movie (Indiana Jones and the Last Crusade). The touch made it through about 1 hour and 50 minutes then the battery crapped out. None of these times are close to Apple's estimates and what some reviewers are indicating.
This particular reader disclosed that he ran iJailbrake on the iPod touch and installed some third-party applications–which could be the culprit, but I'm not sure.
Update: The reader quoted above clarifies the process of problems with his touch battery:
1. Ran iPod Touch as shipped from Factory for several days. Battery life terrible. 2 to 3 hours max when I got a message battery life was low.
2. Ran the iJailbreak hack and battery life was no better or worse.
3. Restored iPod Touch to default settings and used for another day. Less than an hour of listening to podcast (PowerPage Podcast), showed friend the features over lunch. Listened to remainder of said podcast and got the warning of less than 20% of battery life remaining.
4. Did a full recharge upon returning home. Disconnected from charger and started movie (Indiana Jones) got about 1 hour and 50 minutes when the iPod Touch turned off.
Update 2: One reader pointed out that CNet's iPod touch review by Donald Bell has been updated to include battery life data resulting from CNET Labs' testing.
Our CNET labs found that the iPod Touch lasted an average of 23 hours for audio playback and 6 hours for video--which is better than expected, and more than adequate for a few in-flight movies.
There is a possibility that the reader above received a bad unit (which is bound to happen) and should get it replaced.
If you have an iPod touch, leave a comment in the TalkBack with your battery life results (with and without third-party applications installed).