That is also happening with some guys on the CM12 Roms. Hasn't happened to me personally tho.It takes a week or 2. I had poor battery life then suddenly it shot to 25 - 28 hours of usage with a good 5 - 8 hours screen on time, depending if i have wifi on and 3G off etc etc.
Does anyone else have issues with Youtube and html5 streams freezing after 40 seconds and having to restart the stream to get it going again?