Id keep changing the diff fluid every 500 miles or so until you stop seeing metal shavings in the fluid. No set times, each install goes differently.

 

Makes sense to me. I don't think it's about something that is going to happen, rather just wearing down burs and sharp edges on the areas that oil can't create a buffer between. Think a new key in a new lock, sometimes you have to break it in some and wear down the sharp clean edges before it works smoothly.

Check and clean it out often until you don't see many (if any) shavings.