Or, they may have intentionally mess up the battery life to force us to upgrade to the 5s/6? Wouldn't be the first case of their deliberately dumbing down "old" models when releasing major OS upgrades, to put it mildly...
They continue to sell the 'old' model at full price right up to the day the new model hits the stores. My iPhone 5 was barely two months old when iOS7 was released and to me, was still a source of 'new' enjoyment. Apple drained that, along with the battery...
Anyway, I'm over it now. I learnt a big lesson - never 'upgrade' from the o/s my phone ships with. Ever. I rarely use any of the 'new' features anyway, and can easily live without them. If Android wasn't such a privacy free zone I would jump ship after the way I've been treated with my iPhone 5, but sadly it looks like I'll be staying with iPhones for the forseeable future. Not happy about that right now!
I had a play around with my partner's Android phone the other day and although it's a nice bit of kit, and better than my iPhone in many respects, I can't abide the lack of privacy. Even installing something so simple as a flashlight, the app asks for access to your internet history, call logs, contact list, location, and data plan before you can proceed. Decline and you end up with no apps!