Your probably right, I exaggerated the hours, but it was probably about 100 flights.
It is worth checking every winter becasue the aluminum will wear against the steel.

Your muffler extension is interesting, I searched the catalogs as well. I played with home made mufflers from brass drain pipe and tubing, but my soldering techniques stunk and the joints fell apart after the engine heated up. I used silver solder with a MAPP gas torch. Someday I may try Brazing rod if I find a source and read about technique. I've stopped trying, for now. The benchtest was bordering dangerous with a rotating prop and pieces of warm brass falling off the muffler.