Bluetooth and battery life

[Astro_Digital]

How much does using bluetooth cut down on battery life?

[Rolow]

My 3GS went from full charge to a quarter charge after 5 hours use with a set of Sony bluetooth headphones. That was for music listening only no video no phone use and no 3g use just bluetooth music.
I used the 3gs bluetooth two days in a row with the same results. Then I started using the bluetooth adapter that came with the Sony headphones and under the same conditions I was left with a 3/4 charge on the phone. The odd thing is the Sony bluetooth adapter uses the phones battery for power it does not have its own power source.

Here is a link to the headphones i use. They work fine with the 3gs but when you plug in the adapter the phone gives you the message "This accessory is not made for the iPhone would airplane mode" I reply no and every thing works fine with music and will ring through the headphones and the phones speakers if you get a call. You can not answer the call through the headphones and the mic does not work.
http://www.amazon.com/Sony-DR-BT21IK-Wireless-Transmitter-Bluetooth/dp/B000ZN041C/ref=sr_1_1?ie=UTF8&s=electronics&qid=1246030081&sr=8-1