For what it's worth - Duke Fox said a few years back that 200 hours was a good life expectancy for a good model engine. That's been a while back and I'm sure you will hear from someone that they have an engine with four times that many hours. Of course it's had three new cylinders and pistons, two new cases and a couple of crankshafts. Modern materials have lengthened the useful life of model engines in the last few years. Unless you keep log on all the run time you'll never know for sure.