These little engines seem bulletproof. I am running 3/4 auto & 1/4 LL. That gives me the lead content of old 80 octane, and seems to ameliorate exhaust seat problems. I would never admit to using a dollop of MMO at each fueling.
Remember, we do a compression check every single flight. A Mooney gets a compression check once a year. On average, a cylinder goes bad at the six month point.
Also remember - a cylinder can go soft with a piece of junk in a valve seat, and may fix itself the next time out. Shops often yank cylinders prematurely, and on these old engines the cylinder shop will red tag it in a heartbeat.
I have had three cylinders crack over 60 years. I am replacing one today. Even with the crack, it developed full power. We watched it for two weeks before I hooked the air to it to see what was going on.
A small Continental will run forever with care - or you can pull it apart and spend $20 grand - your choice. I have had excellent luck over 6000 hours behind these things.