I was recently caught up in that midwest Ice fest and lost power for a couple days. So, knowing my trusty Zune had a radio tuner, I plugged in my Creative Audio external speakers and was able to listen to news etc. Now, this was at about 7:30 or 8 at night, I had been using it on and off during the day, and I figured for sure, it would be dead by morning but atleast I would have some tunes to break the silence during the night. I was amazed to find out that next morning (about 9:00) my Zune still had a quarter of battery life. Now, the speakers are self powerd BUT, I was still impressed with how well it did. BTW, I highly recommend http://www.creative.com/products/product.asp?category=4&subcategory=29&product=14061
these speakers. Amazing sound, I like listening to music loud, and I have had the same set of AAA batteries in it for a month or more!