My commuter sees 6000+ miles/year.
The current rear wheel has reground cones. As of 15 000 miles or thereabouts there are no undue signs of wear compared to unground cones.
So I don’t know. The argument about case hardening makes sense. But it is not supported by my experience.
I had a go at case hardening reground cones before use. Quite tedious.
But friends in the automotive business laughed at me. ”things that small gets hardened through and through” they said.
So I tried installing some fresh off the grinder, and it seems to work just fine.