Call Diesel Electric in Casa Grande, AZ ( no toll free number)
And order you a starter contact replacement kit for less than 50 this will solve many problems. Likely the starter soleniod contacts are worn and the current won't go thru to engage the soleniod and thus the starter.
Sometimes after replacing the contacts a tired starter (one that had other internal probs. ) will fry a short time later.
Replace the contacts and then at least haul to to auto zone, read your parts store that tests starters and altenators for add'l bad components etc.
DC usually gets 350 - 400 for a reman starter.
Diesel electric sells new ones for 350.
On the mileage question, most trucks may act up at 100k or so depending on how much you start and stop.
I changed one on a contractors truck recently at about 70k, lots of short trips etc. .
Good luck
Andy