there are rumors that the 1.1.3 firmware for some reason has bad power managment and that the battery life is much shorten than under 1.1.2.
but, in the end, if I use the ipod for more than music, I charge it daily as well. the ipods battery just isn't that good. if you use it a lot to play games or something so if the display is on a lot or if you use wifi to install/uninstall things, maybe play a round of tap tap revolution here and there and surf the web a little and boom your battery is down to 10% ...
if you want to know if everything is right, just set auto-lock to never, turn wifi on and surf the web. best thing is to use a website thats constantly refreshing itself. if you get something around 3 hours of battery you're good.