I have both a 2G 8gig (new Sept 07) and a 3G 16gig (new Nov 08). Battery life is extremely subjective to what you are doing at the time, and not withstanding what you may have loaded and/or running.
I can easily kill the battery in either in less than 1-2 hours (watching movies, games). But....the norm is that I charge them in the evening (7-8pm), then can listen to music all night, and then use the phone all the next day (averaging about 5-6 hours of usage) and still not hit the 20% reminder mark by the next charge time. Rinse and Repeat for over a year on the 2G.
My wife's 2G will easily go 2-3 DAYS without needing to be charged. It's more used as a phone than a internet/email/game/business gadget like my use.
FWIW. YMMV.
