SO I just bought myself a IPhone 4S on Sunday. I bought it at about 1pm in the afternoon (only at 65% battery power) and only sent a handful of text messages and only added 3 contacts that day; by 10pm thats night I still had about 35% battery life and put it on the charger. I took it off the charger at 6am Monday morning and added all my contacts and did some text messaging, one phone call, and put my phone on the charger again at 30%. Tuesday morning I took it off the charger at 6:30am, downloaded about 15 apps, did some texting, no phone calls, and my battery died by 2:30pm in the afternoon. So at 4pm I plugged it in to charge and left it all evening and throughout the night, took it off this morning fully charged, Ive texted a fair amount and played some games and noticed the battery was still dropping faster then my blackberry ever did. SO I did some research and talked to a tech person who explained how when he reset all his settings (General-Settings-Reset-Reset All Settings-accept.accept.accept lol) that he found his battery power to improve slightly. SO I did this-you only loose anything that hasnt been backed up, your contacts are still there as are any apps/games you have downloaded; I also deleted any "free" apps I downloaded(could have cookies which eat up your battery life for no reason), disabled Siri(can always enable her if I need to) and right now my battery after rebooting and everything is still at 50%. I will let you know tomorrow how it did throughout the night but perhaps try this, it can't hurt anyways!
Hope this helps!
Til Tomorrow!
L_x0x