Dar -- I know. One of my hobbies was auto slalom-racing & I used twin-cam Fiat 124's -- 8,000 RPM+ from 125 - 175 HP 1,400 - 2,000 cc engines, which means MUCH greater reciprocating loads than model engines. However, cars are hardly a reasonable comparison. Full scale recip AC engines & auto-based boat engines run at much higher loads than cars & they typically have 1000 - 2000 hr TBO.

While boat engines typically run ~ 4,000 RPM, the recip masses are absolutely gigantic in comparison to model engines, so I don't accept your contention that fatigue is a serious model engine problem. It may very well be the lifetime limiting factor, but the lifetime is plenty long enough, especially considering the low replacement cost (unless it's OS we're discussing -- short life & high cost).

I'm not sure what you are trying to establish. I have 6 TT 46 Pro's with over 100 hr each, & the highest time example is ~ 180 hr. That's the story. They all run very well, despite the high time & every one is a one-flip starter. Performance-wise, my experience is similar to XJet's -- they lose ~ 400-600 RPM from new -- & that seems to go on forever. I don't know what "forever" is, but it is one hell of a lot of air time & I certainly don't plan on buying any more less-than-forever OS engines in that size range.

Perhaps a significant factor is the use of fuel with castor oil lubricant (Omega) -- that's essentially all that I use