Umm... it depends. That's about the best answer anyone can give. When we traded the old 1480 it had just over 4000 hours and it was well past time to get rid of it. We were lucky to get in two days without a breakdown. We could have completely rebuilt the thing and got a few more years out of it, but it no longer had the capacity we needed and wasn't worth the money for major repairs. The 2388 that replaced it is 17 years newer, but had almost 3000 hours when we got it. The 2388 had a bunch of work done on it, though, and many of the wear items had been replaced. Aside from a few minor things it has been a very reliable machine for us.
Have a 96 2188 with 6100/4300 hrs on it, I'm the 3rd harvester to own it. Yes lots of parts replaced, some for the third time. But on the other hand it would surprise you at what is still original. Its been a very good machine. I plan on running it hard for at least another year. The only thing that scares me is the electrical, but so far it has proved to be reliable in that department. Keeping them super-clean and blowed off every day I think helps the life of a machine more than you might realize.
Just for fun, do the math, at 4300 rotor hours, say avg. of 8 acres/hr (low end) and say avg. yield of 40 bpa (low end too, this machine has done lots of corn) that's 1.37 million bushels. Double that number if you wanna get closer to the real number for the corn its done, that's like 2.7 million bushels! Now that's alot of grain through one machine, I don't care who you are.
neighbor likes buying cheap, and does all his own repair work. got a high 5 or low 6000 hour 2188 with money dumped in it for under $20K. we know a guy that is running the single family owner (his dad bought it new) Gleaner L3, and it is over 10K hours.