My advice for better battery life: Never do on OTA update, download the ipsw and restore from iTunes. Just google ipsw and download the right iOS version for your iPhone. For those who don't know which ipsw to download, connect your iPhone to iTunes and check if it's an iPhone5,1, or iPhone5,2 or 6,1/6,2.
I have seen better battery life when I do a normal restore from iTunes using a downloaded ipsw, not a DFU restore.
Hope it helps.
Normally I would say this advice is rubbish but you're actually spot on.
I updated my iPhone 6 to iOS 8.2 OTA and experienced poor battery life. So I downloaded the ipsw and restored using iTunes. Recovered from my backup and battery life has indeed improved.