Wirelessly posted (8800: BlackBerry8800/4.2.1 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/102)
That's prety darn good use, that long. It will vary of course from user to user and according to the applications in use.
You should be topping off your charge whenever you get a chance during the day and charge it at night. Don't continuosly run your charge down to nothing.
Read the FAQ "Maximum Battery Life" for more info. http://www.blackberryfaq.com/index.php/Main_Page