So, does the coatings hold up better then the old age header paint? Do the coated headers hold up better then bare steel headers?

The number of heating and cooling cycles, the temperature range the headers see, the fact they hang down under the chassis without protection, are all things headers have to go through. That has to make it hard for any protective finish to endure.

Stainless steel header tubes get brittle and the tubes tend to stress crack.

The header business has always had long life issues. One really only needs to look at how many cast iron exhaust manifolds have failed over the years, and one might give headers a bit of a break.