I dont have the 4S but the specs are pretty much the same but I have the ipad 2 and with no problems, though I dont see the iphone 4S giving any one any problems either
I've been hearing that about the 4S.. Are you keeping your apps shut down when you're not using them -- double click the home button to see your "running" apps, then shut them off.
Try and factory reset the unit and start it as a new phone. I would unplug my phone at 7 am and by 12 it was at 50%, did the reset and it's now at 75-80%