Use and abuse coupled with TLC - all make a difference.
I bought a 58 MF65 four years ago that was working with no apparent problems - with just 10,000 hours on it. Today it has just under 11,000 hours on it. I have done only routine maintenance (grease, LO and filter etc) to it, When I first got it I drained and flushed the tranny and then put new oil in. Replaced shifter boots, tie rods, a few belts, plugs (gas engine) and set timing and valves and adjusted clutch and brakes..
The tractor runs with no oil leaks, no fumes or smoke from exhaust or blowby and does very well in the winter (-25F). It is not unusual to find farm tractors with high hours. I expect a large majority of those machines are worked hard and most seem to do well and survive.
Whether or not the new machines will do the same service remains to be seen.
J.