On first trial... simply turning off "mobile data always on" nearly doubled my battery life.
I was getting 12 - 18 hours before, now upon first trial I got 28 hours.. would have been longer if I hadn't played with my video camera for about 20 minutes.
Menu, settings, wireless & networks, mobile networks, uncheck "enable always on mobile data".
Unless your trying to use google chat of friends or some app that needs a constant data link you won't know the difference.
My gmail and text still work perfect.