Interconnect Break In?

@jasonbourne71 " What does change over time is the contact resistance of the connectors due to oxidation.” +1

Simple unplug-plug the same cable changes contact resistance dramatically! Always check your contacts under microscope of just magnifying glass, what you’ll see might shock you! Contact surface is another problem, often “gold plated” contacts are much worse than pure Cu, due to high resistive metal under it (Ti, Ni etc). I found recently couple of very good Rhodium plated receptacles and plugs, showing very low interconnect resistance, and no scratches after use! Remember as contact established by two parts, thus these parts should match in terms of plating metal, ideal metal pressure etc. 

Cables from resistance standpoint are getting worse with time. Dielectric (bad one) hardens and changes Er/TanD after few years of use, which significantly degrades phase velocity flatness across audible frequencies. The lower dielectric constant is, the better! Shorter audio cables have less audible sensitivity to phase velocity than longer ones. 

@curiousjim imagine cable production / assembly line with last step check before selling to buyers, assuming all cables are different, even the same brand! 

"Instructions in Cardas box clearly state ""through use (after 150-200 hours) the dielectric materials will build up a uniform charge” 

-that only can be true for cheap dielectric, which cures (hardens) with time, faster at high temperatures.. audio signals are low level AC signals, not affecting dielectric at all. more expensive dielectrics used for stable testing results use time-stable dielectrics (Polytetrafluoroethylene  PTFE, Gore cables, etc).