Bought a flight school 172, motor is 300snew installed in 2013, but sat for a few years, ground run in annual but no more time then that. Pulled valve covers some rust on springs but nothing crazy, I scoped acc case gears after I got the mags off, light surface but no pitting. My IA said run it and if it makes metal in 100hr I can split it and he can rebuild with a new cam and lifters. I typically do oil and filter changes every 25 hours and typically fly 50~ per month. What’s the risk to the engine when the lifters start to wear, am I looking at damage to the main bearings and case?