My daughter started using her iPod Nano (16GB) with some 3rd party in ear ear phones and found that the battery discharged fairly rapidly - half down after 4 hours. We've completed the Apple test with the original ear phones, and it lasted 24 hours as Apple advertise - nearly to the minute funnily enough, so the iPod is working as advertised. To my mind, three factors could be causing the lack of power... 1. Different (3rd party) ear phones being used, although we're testing this now using the 3rd party ear phones with the Apple test, and so far it looks to be lasting well. 2. Volume - she claims she uses the iPod at 2/3rds volume, whereas the Apple test is at half volume. 3. File format - Apple say to compress the files at 160kbps, whereas I usually compress MP3s at 256kbps. I'm guessing that the main factor will be the volume. Will the file format actually make much difference? She claims that the volume levels at half volume between the ear phones are comparable, so if volume is the issue, can one purchase more efficient ear phones which will make the iPod battery last much longer? I'm going to be running tests, but I'd be interested if people have already made their own conclusions about this topic as it might save me some time. Thanks for any replies.