Thanks boss EarlZ for the info but recently my phone has been
running on battery for 11 hours using only 21% of my battery,
leaving 79% remaining battery for my SGS2.. hmmm...
my SGS2 must have been scared of the idea of being rooted. hahaha..
anyway, what i remembered doing before i got this better battery performance
for my SGS2 was that i deleted/uninstalled my pre-installed yahoo msgr app, which was
always running as a service on my system.
then i removed(from idle screen and stopped in running service) battery widget apps
which is also running as service. and other unnecessary running apps was stopped.
I then recharge the phone to 100% then tested it. then yeahey! it worked for me.
the Android OS battery consumption dropped from 90%->80%->-70%->49%->17%(lowest i got)
2 days of battery life is OK with me.
I can now wait for a newer firmware that possibly could extend my battery life longer.
To all, try this, this might work for you.