When I started experimenting with my Motorola V635, I tried out a few bluetooth devices. I noticed that leaving the Bluetooth connection On, would often take the battery level from full to low much faster than normal. So a good tip is to always keep your Bluetooth connection Off unless you are using it. It might also be a good idea in case someone gets a good hack for sending/receiving files without permission. Then someone could take files from your Bluetooth-enabled phone/smartphone/PDA or even worse, send a virus-type file to "brick" your device.