My light came on at exactly 10.0 hours. Did the service (all but the valve adjustment)at 11.5 and reset it. I am up to 21 now, and will be doing the valve adjustment this weekend. I saw so many posts of the valve clearence not opening up at 10 hours, I figured I'd wait. I still don't hear any valve noise in it, but I'm thinking I have held off long enough.