I see lots of combines on used lots with 3000 to 4000 hours on them, and it seems to be regardless of what model year. Just how many acres do y'all get per hour on these machines? I'm trying to get a feel for how hard the use is on a combine per engine hour... I've got a pretty good idea of what an engine hour does to a tractor, swather, baler or balewagon, but I'm utterly clueless about combines.