Tractors are built to last.  I first got into farming in 2000, and my first tractor was a 1951 Ferguson TO-20.  A great little tractor that I used for 14 years and sold for more than I bought it for.  A year after I got the Fergy, I knew a needed a bigger tractor with a loader and I got a 1967 Oliver 1550 with a loader.  I really loved that tractor and it served me really well until water got into the hydraulics and I bit the bullet and bought a brand new 46 horsepower Kubota with a cab and loader, whcih I still use today.  Even with the hydraulic problems, I sold the Oliver for EXACTLY what I bought it for.  Along the way I also bought a 1980 large (88 horsepower) Ford with a loader.  My point is tractor really last and if you take care of them, that will last for many decades.