Something's really wrong with your phone if it drains 25-50% overnight. The standby time is measured in days, it should not drain so quickly.
I had 100% when I left home this morning and after a 1.5 hr commute and maybe 30 mins playing music, I was left with 60%. Although I can turn more stuff off, there is nothing on the Iphone 5 that wasn't running on the Iphone 4 (apart from siri)
I don't know where the days estimate of standby time comes from as I doubt I'd get through the working day!