I put the CM9 ICS on my rooted kindle and yes, my battery drains a lot faster, even when I'm not using it. I like ICS on it too much though, so I'll deal with it for now. Also, I got mine refurb for 130$ and rooted about a week or 2 after I got it, so I don't know if the refurb battery life was short anyway, for sure shorter now after root though.