To get the audio to pass back thru most of us have been using a program called audio.exe or BTaudio. I'm not sure what phone you are using.. so I can't tell if this would be what you need.
If you goto the fourm:
http://www.ppcgeeks.com/transfer-cal...set-t1559.html
That is where I posted my Caller ID to BT headset (tells you who is calling in your BT headset) program.. in that program I have the audio.exe also.
So what I do is either use the PPC to open media (tcmp, ect..) or press the BT button and say 'play "artist"' then I just press it again and say "open audio" to run the audio transfer to the headset.
Hope this helps,
As for the battery life, I'm not sure, sorry.