I have never had a bearing problem with any pull type trailer. I would estimate that I have pulled well over 100,000 miles since 1961. My secret: Remove bearings once a year or every 3 to 5 thousand miles, clean and inspect thoroughly for any visible signs of wear, repack properly using only high temp bearing lube( my current favorite is Mystik JT-6).
If there is any signs of wear, replace only with a bearing made in America or Canada. I have seen many bearing problems with components made in China, Tiawan, and Mexico.
Even though you are told that they are the same and as a retired design engineer of 41 years experience, it is my opinion that they are inferior.
It is my opinion that a majority of axle bearing problems come from:
1. Losing track of when the bearings were last serviced. ( keep good notes and hang these notes in plain view on the wall of your garage.
2. Overtightening the axle nut. Leave a slight amount of play in the bearings. Overtightening results in heated bearings and failure.
3. Not keeping rear seals in excellent condition. I know many folks that replace them every time that they repack bearings. I always inspect the seals and replace if defective.
1984 Coleman Estimated miles pulled 40,000 miles
2003 Rockwood Freedom 1000 miles
1999 Heavy Duty Utility Trailer 15000
1961 Light Duty Utility Trailer 40,000
1977 Airstream 35000