current passing thru cables causes heat loss no matter how minute, this is inescapable....
perhaps this is one reason using heavier gauge of wire makes sense...
alternating current passing thru cables have this "skin" effect,
but in the high megahertz regions, no for audio frequencies...
a number 18 wire is good up to 21khz when considering this skin effect,
that is why several strands of smaller wires as in a cat5 cable is immuned at this frequency...
when exposed to air, copper reacts with hydrogen and becomes tarnished,
that is why silver plating helps...
when exposed to air, several plastic insulations lose original consistency and hardens and discolors....
there is no escaping this, in time you have a cable that is not pliant as the day you first got it...
may even have changed in color and has become stiff...
that is why replacing then when they show signs of wear can be a good thing..
or perhaps redoing the end terminations can save you from buying a new one...
i read advertisements by manufacturers....they are all meant to sell, not to educate...
i have seen this effects from making house calls on rich clients having these cables...
they buy new ones and give the old cables to me, para tansuin...