Yeah, iOS's background processes (that's the key word) are very efficient.
I wish that I could help, but I am not experiencing that. My iPhone is functioning all the time, and I only charge it when I go to bed. I unplug it in the morning by 7.00, and charge it at 23.00-23.30. In-between, i play music and games, chat, iMessage, Facebook, YouTube, surf the Web, etc. When I plug my 4S for its charge, there is around 10% left.