You know, ever since I got this phone I've been hearing that you need to condition your battery... but having done a bit of reading I'm yet to see a single expert say that you need to 'condition' li-ion batteries.
In fact most say that you don't!
I think this belief is just a relic of the days when batteries actually did
need to be conditioned, and it's perpetuated by the fact that battery life appears
to improve after a week or so... but I reckon this is just due to the novelty wearing off and the phone being used slightly less.
I'm 100% certain that if I were to really hammer my battery today, I'd get as little usage time out of it as I did on the day I bought it.
Apparently discharging the battery fully and then charging it fully can help if your battery's circuit is misreporting the charge, but other than that I'm calling shenanigans on this whole conditioning myth.
edit: Also, check out this thread and see if you're having the same issue as these guys
Partially solved: Potential cause for excessive battery usage - xda-developers