My battery tends to last all day before I need a sleep to recharge
Dave, tell us what sort of battery and the equipment it goes in. Otherwise it's a case of how long is a piece of string mate...
Given his recent threads, I'm guessing he's asking for the standard battery life for a 450D.
500 shots at a guess - i'm telepathic!
According to this review here you should get at least 500 pictures out of a battery unless you use the flash for every shot.
Would anyone consider using a non canon battery from 7dayshop.com? 2 for £10 sounds too good to be true so I am sceptical as with all things like that.. There can occasionally be exceptions though.