The battery on my 920 is pretty good. Only time it really drains is if I'm watching a lot of youtube vids at 720p.
At average usage with 3 emails (2 synced hourly 1 as items arrive), whatsapp, checking up on news, watching a few videos, checking on social networks, I get solid usage. At least a full day. WPCentral and Whatsapp are the only other background tasks at the end of the list:
If battery is that bad, it might be worth taking it back or getting Nokia Care Point to take a look at it. Should still be under warranty.