FWIW when I was selling an extra motor I aquired everybody asking about it was interested in how many times it had been overhauled. Their opinion was anything more than three times and the case is suspect.
My mechanic, remember he's a cranky 70 year old who was chief mechanic at Whidbey Island NAS (and can prove about 200 o-200 rebuilds from his logs), said that after about the 3rd rebuild the case fretting and resulting resurfacing leaves the case unusuable. If that doesn't happen, the resurfacing of the cam bores (no bearings remember) makes that unusable. He said he's never seen a case beyond 7 uses pass overhaul inspection at the machine shop. Genenerally they fail at 4th or 5th overhaul. All this depends on the previous assember to pay attention to case mating and proper torque of the bolts to reduce fretting (the two halves rubbing together) to a minimum.
Your mileage may vary of course. Mine is newly on the 3rd overhaul and I don't suspect I will ever see the 4th.
