I think the problem lies with the fact that since the YS engines make such big power, everyone wants to load them up with huge props which keep the noise factor down for pattern flying. This in turn makes the engines run so much hotter which takes a toll on engine life.
We have field reps who have 300 plus flights on a couple of the DZ engines with virtually no changes in performance. Admittedly, these guys are experts who know how to set engines and seldom have leans runs.
I believe that running less load will make any of the engines last longer. Maybe you ought to try it.

Good Flying,
Dave