So last Sunday suddenly I had a horror situation where battery when from 85% to 25% in 2 hours sitting on idle. I searched like mad all over Apple Communities and other forums to see if other people had "iOS 9.2 battery drain" and some did. On the 2nd day not only battery drain but the App Store was non-functional. It took me a few days to figure out how to manually revert to iOS 9.1, but I did. Not without a huge hassle. I had assumed that iCloud backups would take care of the restoration process so there would be "no muss, no fuss". But to my chagrin I found out that iCloud backups only like the last several and they were all iOS 9.2 so INCOMPATIBLE with newly restored iOS 9.1 iPhone 6S. So I had to re-download all 70+ apps and sign-in to them.
lessons learned:
* I won't blindly trust Apple on OS updates anymore
* always make an iTunes local backup of your iPhone regularly and especially right before doing an OS update
P.S. Into my 3rd day of restored iOS 9.1, battery life is a DREAM again. I got to 51% when I put it back on charger at 8:45PM after taking it off at 10:10AM.
lessons learned:
* I won't blindly trust Apple on OS updates anymore
* always make an iTunes local backup of your iPhone regularly and especially right before doing an OS update
P.S. Into my 3rd day of restored iOS 9.1, battery life is a DREAM again. I got to 51% when I put it back on charger at 8:45PM after taking it off at 10:10AM.