Airedale, it's a little difficult to correlate hours with condition with tractors just as it's a little difficult to correlate miles to condition with cars. A lot depends on how it was used and how it was maintained. I know farmers with big tractors who figure 7k to 10k hours before any major work, like an engine overhaul, is needed. One of my friends bought a John Deere from the dealer with well over 7k hours on it and the dealer had just done an engine overhaul when he took it in trade. Another neighbor bought a 25 year old Oliver with over 5k hours and as far as he knows (which ain't much of course), it's never had any major work and he's been using it now for a couple of thousand hours. An awful of the smaller tractors are owned by homeowners who are only going to put 100 to 200 hours a year on it. At any rate, personally, I'd expect a properly maintained tractor to go over 5k hours before needing any major work, and of course that's just my guess.
And welcome to the forum. Since you didn't put much in your profile, for all I know you may know a lot more tractors than I do. /forums/images/graemlins/laugh.gif