Great work.5000 hours is realistic for many brands of mowers if well maintained. Currently have an '04 full sized turf tracer with 4400+hours and it is on the original engine. Clutches last around 1000 hours, belts should go at least 350 hours. Those numbers will vary with the brand and operating conditions.
If it's got a Generac, it might go 3500hrs+ before a rebuild. I've seen 4000 hrs plus on those motors.I have a 1999 72" Dixie Chopper with close to 2500 hrs. on it and it still runs great. I know the first hr meter went out with over 1000 hrs but i don't remember what it was at. Then it didn't have an hr meter for a while and now the 2nd meter is at 1200 and some. It should need the motor rebuilt at some point but it's still running strong for now. And even then I'll just order the rebuild kit and have the cylinders bored over and have maybe 300-350 bucks in a rebuilt engine. I also have two newer Dixie Choppers but I just can't justify replacing that old one since I'm sure it'll keep goin for a long time still.