IOS 4.3.x is it the reason my battery dies soo quickly ?

There is two iOS devices both are the iPhone 3GS , both are on the same firmware .
Ever since updating to 4.3.x our battery drains too fast, my phone was on standby most of yesterday . It’s battery went from 80% to dead in a few hours .
Screen brightness is low , 3G and data is off I mainly read emails and twitter a little . ..
I do the exact same things if not a little less now , compared to when I was on iOS4.2.1 .
4.2.1 seems to be the best iOS firmware for battery life , wish I could go back to it…
Why would Apple make such a change from one Firmware to another .
Now our phones have to get charged every day .

Is anyone else having the same issue with 4.3.x ?
What is recommended ??