I thought that you might be entertained by this. My heads are marked HQ5991. My odometer reads just over 110,000 miles. Attached is a dyno sheet after I did some modifications to the Thunderheader. I think that my bike is a good testimony to the life expectancy of your products. Would you like pics of the combustion chambers or anything else when I tear it down? If you notice the dyno sheet, it only had 105,000 at the time. Feel free to post it if you would like. For the record, they have not all been easy miles. I'm the old motocrosser that you spoke with 5 or so years ago.