Today I officially stopped my research in the battery drainage bug for the iPhone 4S under IOS 5.X. I can't go any deeper nor make it any simpler.
I'll post my results tomorrow.
Today I started trying to get rid of some other problems I'm having with my iPhone and iTunes : the nasty iTunes sync behavior : I'd keep getting the apply/revert buttons pop up for my iPhone 4S. My iPad doesn't do this...
During my search to get rid of this, I bumped into something else that was weird and what is more amazing : it is linked to the wifi sync malfunctioning behavior.