Do cables age or become too old at any point?

It should probably be pointed out that the corrosion visible through a clear jacket maybe wasn't caused by the jacket itself, but was the result of such an old cable's having been made using copper that was not pure by today's standards. My head hurts now....

I have seen and heard for myself what Sean describes about oxidation over time that is visible through a clear PVC jacket, and the degradation is quite audible. I imagine that this eventually happens to a greater or lesser degree with any cable. But it seems to me that a Litz-type (individually coated fine strands of wire within a braided geometry) cable, such as the Cardas I use, should have the longevity advantage.