Sorry that I don't have the time nor bandwith to argue the old stuff re expectation bias, blind studies, anecdotal experience. I CAN tell you that in the 70's I had extensive experience with molded and machined very expensive PVDF (fluorocarbon) structures used in laboratory measurement tools. We noticed that these structures migrated slightly over many months, sometimes even cracking!
Thermally retreating the product housings before or after assembly resolved the problem. End users (hospitals, research labs) were advised a DIY in-house corrective procedure. Som I learned that although we knew that softer "Teflons" indeed "cold-flow", even the very hard and supposedly completely inert iterations migrated across time unless the formative stresses were released.
So when I provided a few hundred A'goners cheap all-Teflon power cables, boxes, and DIY Kits years ago I took the trouble to thermally process the raw Cu/Teflon cable to assure no audible break-in from a non-fully cured dielectric. My contenbtion is that the conductive metals used in our audiophilia aren't what require burn-in, but the associated dielectrics. Too bad we couldn't just build devices without ANY insulation, eh?