i have everything set to minmum and my display on my Galaxy S2 is on 40%,this is normal right?

what is good battery life and how long should it last me,kies said that my phone is up to date on everything,im on Android 2.3.5 GINGERBREAD
open menu, settings, about phone
now please post what firmware you have
it is some sort of.a.serial number that should end with 2 letters and a number example.KE3
baseband is I9100XXKI4

kernel is 2.6.35.7-I9100JPKJ2-CL655700
ROOT@DELL143 #2

build number is:
GINGERBREAD.JPKJ2
you are updatet so battery should last a little longer but that's it. Now my advice to u is to.actually set the brightness to zero.which is more.then enough.in indoor places, and only choose higher brightness under direct sunlight.
you can download a.brightness widget for easier application.