After upgrading my firmware from 3.12 to 4.37, I discovered a tremendous boost in my battery life. My battery use to last in standby mode for about 12 hrs, with 4 or five voice calls of 3 mins, and bundled with 15 mins of GPRS session. I use to charge my battery two times a day. But after the firmware upgrade, my battery is on turbo !!. Now, based on the same usage as above, after 24 hrs, only one bar has come down!!!. Can this be possible ???

Yes it can, and usually does.

Smarter usage of the cpu from the os(firmware),I think. And by the way the wap browser on firmware 3.16 is very buggy...

After reading this, I think I MUST upgrade my firmware, I'll go see what NSC I've got closer. (My phone runs under v3.16, shame on me! :) )