The big factor in cylinder wear is dirt ingestion, and the old oil bath air cleaners or the even less-effective wire mesh ones let a lot of dust and dirt through. Add some more dirt through the slots in the valve cover and down through the crankcase thanks to the road draft tube, and those old engines literally bored themselves by abrasive action! A re-ring was common at about 30K, and another at 50K or so. A rebore would be needed at 70-80 with the third ring job.
It's extremely unlikely a standard-bore engine would survive beyond 70K miles, let alone twice that much.
Jerry
