iOS 6.1.2 Battery Drain Issue Test

My iPhone battery was good up to iOS 6.0.1, with 5 hours of usage (2G) and even up to 5 days on standby! After upgrade to 6.1, it loses 2~3% battery every hour on standby (Wi-Fi and 3G off) and only lasts for 1 to 2 hours of usage before dead. It is not as bad as some who report losing 10% of battery every hour on standby, but to me, the battery life has reduced to a quarter.

I have gone through many suggestions and solutions from reset and restore to using old backups and so on, but none of them worked.

With my recent test, I am almost sure that the bug is in iOS. I charged the phone to 100%, unplugged it and set the Airplane Mode to ON and guess what? It is 5 hours now and the battery is still on 100% of charge!

I am using 2G network and the signal in my area is very good (full antenna). I think the problem is in communicating with the BTS towers and nothing related to apps or settings.

It is obvious that the Airplane Mode saves battery, but in recent iOS updates, it's 2G network that ***** battery more than usual.

Are any of you with battery drain issue have tested this or may test it and report the results?