doubled my battery life
I think I've found the biggest problem, at least on my phone..
I went through all the battery optimization steps but I couldn't ever get more than 10-11 hours.
Well, I went into Settings->Apps->Manage Apps->Running Apps and killed off a few (Facebook, Footprints, Stocks, and NASCAR). All of the apps except NASCAR restarted themselves. With NASCAR not running, I'm easily getting over 20 hours of battery life.
I've narrowed it down to just that app.. it's the only one that stays off when your force close it (until you turn your phone off, anyway). Ever since, every time I turn off my phone for whatever reason, I force close NASCAR as soon as I turn it back on. Now my battery is lasting 20-22 hours.
I wish there was a way to just remove that piece of crap application without rooting the phone.
Also, I've noted that WiFi does NOT use less battery power than 3G or 4G (despite what the battery optimization thread here says). It just sucks the battery dry, so I keep it off.
Your mileage may vary, of course... Please post and let me know if it works for you.