I've got an old tractor than my father bought new in 1957. The tach/hour meter quit at 9444 hours......IN 1988. I'd venture a guess that it has 15,000 hours on it now. And the engine has never seen major work, tranny is fine, hydraulics are slow, but still working.
I have a 1974 Ford 3000 with over 8000 hours on the clock, and still plugging along just fine.
My Massey 150 and Deere 2440 have 4500 and 2400 hours respectively, and haven't seen much of any trouble between the two.
With good care, 10,000 hours isn't out of the question.
My tractors are 35 years, 31 years, and 27 years old. The "newest one" (27 years old) is like new. I'm looking for something a bit bigger, and will likely get one a bit newer, but condition, not age, will decide what I buy. Age of a tractor is almost irrelevent.
My son has a '94 Dodge pick-up, Cummins diesel, with over 500,000 miles. It looks mighty sad. /forums/images/graemlins/tongue.gif Still running, but beat, broke, and battered.
Under ordinary conditions, todays trucks (pick-ups) are good for 100,000 to 125,000 before they start to fall apart. Some do it earlier than that.