320 operating hours

My John Deere 320 (i believe it's a 1994 model) has approx 975 hours. the mower is original other than the belts, blades, and filters. How many hours does the Kawasaki engine usually run before giving problems? I realize the main factor is the way the operator runs the unit. I'm asking as a general rule of thumb if the mower has been taken care of and serviced properly.

Thanks

320 operating hours