Just finished doing my first full test, and I was pleasantly surprised. I went 11 hours and 56 minutes without charging once, and I still had about 5% battery left. This was with normal usage of Facebook, IG, Twitter, iMore, bluetooth headphones streaming music at the gym and at night, Battle Run gaming, and push emails from my job.
I did notice "Motion Calibration" kept my GPS locations icon on throughout the entire time. I'm assuming this is an iOS 8 glitch, so I plan to fully charge it and turn that off and try it again. I can assume it will go up a bit more.