That depends on how well they were maintained before you buy them. I bought a 1950 TO-20 Ferguson tractor in 2000. I kept it for 15 years. It was a real workhorse. I only sold it because I was mostly using larger tractors and didn't need it anymore. I sold it for exactly what I bought it for, 15 years later, and it still ran perfectly. I actually miss it, it was a fun tractor.