aokp build 31 + semaphore 1.0 (smartassv2 + sio) lost about 1% in 2 hours of idle..
with very light usage (7 minutes of calls and a hour of 3g) i've got 71% after a day(22 hours) of usage...so i think it is equal to gingerbread roms

NEW ICS 4.0.4 EXTRAordinary_4.0.4_beta with default kernel (Glitch B6)

I am proud to say that the battery is really good. My phone usually was out of juice by 5 pm (games, movies, etc). Now it's about 50%!

May b i sud also switch to ics as my battery drains in 12hours. I use 1hour call, 2hr of web surf n may b hour or 2 in playin games. Ryt nw m using faryaabs v7(galaxy s2 looks)

Sent from my GT-I9000 using XDA

If the display is off and DIDLE is active, it could be that you come through 3 days or more, but if you only turn it on for checking Mails or something else the battery is sinking so that you can see it.
I'm with 10% at evening with 1500 mah original SAMSUNG battery if I charged it over the last night with normal usage.
ROM etc. in signature.

Sent from my GT-I9000 using XDA

I am bit confused earlier I was using dark knight 5 it was pretty i was getting around 16 or 20 hours but then I moved CM9 and i my battery drain out of death barely in 8 to 10 hours :'(

is there any stable I.C.S version for long lasting battery???

Originally Posted by MortenJ

What is common battery life on ICS? The reason I'm asking is because my battery only last for about 24 hours before I need to charge again, and it's no matter what ICS ROM I use. I came from Darkys ROM where my battery lasted for about 2,5 days and it's a bit disappointing with the new ROMs.

You should specify your usage. It's almost impossible to say if it's good or bad without the details.

If you could push the battery for 2.5 days(60 hours +/-) ROM/kernel not important, I guess your usage isn't very high.
I have no problem getting 2 days with my low usage on Slim ICS and Semaphore.
But I charge it full every night so I can avoid getting a useless phone the next day.
I can go 18 hours with heavy usage. 4 hours screen, game, surfing, other stuff and a lot of listening to music. I try to dim the screen and use black themes as much as I can.