Mine lasted 100k and was caused by an intermittent break in the solenoid coil which eventually vaporized the contacts. The grinding noise which gradually got worse came from worn teeth on the starter pinion wheel which weren't getting thrown into engagement properly due to the bad solenoid coil. I tried to get a new solenoid coil but could only buy the whole unit. It's a scary expensive $360

 

I, too, have burned through 2 starters in two years, which in the process chipped teeth in my flywheel from not fully engaging. When I had my clutch replaced I had to purchase a new flywheel also, and was told that when inspecting the flywheel during the clutch install (exedy twin disc), that my flywheel bolts were only hand tight, causing me to eat starters. I'm not sure if it had anything to do with it, since I took a chance and disassembled the starter last year, cleaned it inside and out, and reassembled/installed it. It worked flawless for another few months and started having issues again.

I did notice the starter motor had a TON of clutch debris in the housing. Haven't had the issue since last fall after replacing it, clutch/flywheel replaced two months ago.

Fingers crossed...

 

Remember when you guys made fun of the ground kits everyone was installing?

I made my own improved kit over the normal kit everyone sells. 205,000 miles and on still on original starter and alternator.

btw, you most likely have a high resistance issue somewhere in the starting circuit. Check your grounds with a DVOM.

 

I would say change the operator, sounds like they are hard on equipment.