I recently pulled the original bearings out of a 65 ford with gawd only knows how many miles and they were still serviceable.
Bearings will last just about forever if properly maintained and especially, correctly adjusted. Even lousy quality trailer bearings should go a lot further than 70K.
If they're shot now it's because the weren't set up right or greatly over loaded.
On a side note, modern unit-bearing assemblies don't last forever because they are basically never setup right. Even when new they are by their nature, a assembled loose. And of course, they're never repacked.
All just my opinion of course..
