Dude, didn't mean anything by it. I have put togehter 100's in my life. I have never broken one in on purpose. I might drive it 30 minutes and see if it is getting unusually hot, or that it makes noise, but never more than that. The only problems I have ever had was related to using old worn gear sets. sometimes you have to get creative to get them quiet.
I learned from my father who went through his greyhound apprenticiship in the 50's. They put them together pattered them and loaded them up with people and put them on the road. They kept records of every one they built and how long it lasted, so he knew what would last. His book has pictures of "acceptable" patterns that today would be called "unacceptable" in the magazine articles and on this forum. I believe the Ford Shop manuals From the late sixties have pictures of "acceptable patterns" that most experts would today reject. Over the road truckers do the same as do most fleet mechanics I have talked to. There isn't time or money to break in gear sets. They fix it and put it on the road. Never known anyone who raced to break one in. I will bet that 99% of front sets never get "broken in".
Sometimes things happen. Whats the old saying? If you do not ever screw up, you are probably not doing anything.
I put together a 9" for a buddy of mine in high school. (30 years ago) We though we had it good. Nice pattern, no runnout, perfect backlash. I did everythng the way I was taught. But, aparently a carrier bearing race did not get seated good. When he first started driving it, is seemd fine but it started making noise. We took it apart and the edges of the teeth were blue. Backlash was out of spec. The carrier had shifted.
I believe it is a good idea to take it easy on anything you rebuid until you know it will stay together. If the gear set is properly cut and you put it togehter right, it will stay together breakin or not.