how do you exit out of your gps app. do you just hit the red button, or do you use menu > close? if you just hit the red button it is sent to the background and runs continuously. same thing with any media application you run. nothing will kill a battery faster than leaving gps and/or media running. you should get, with moderate to heavy use, several days of standby. with no use you can get nearly 3 weeks on that device.
I do hit close or exit on every media application & web. I don't get several days of standby though. If lucky I get 2 days, and by the end of the second day it will shut the radio off by itself and I can just use it for organizer, or read past emails, etc.