Life span of silver cables with cotton/air dielectric

The whole point of using cotton as dielectric is to loosely cover the wire, so the main dielectric involved with the signal is air. Tight coverings exhibit dielectric absorption (DA), and teflon is the best solid, but not as good as air.

If you treat your cables with something, then that's the dielectric which a signal sees. If the dielectric is not air, you're defeating the purpose of a cloth dielectric.

But the issue with air is oxidisation of the conductors that is unseen and untreatable.
There was a time when most cables were sealed.  I even recall some manufacturers talking about a vaccuum.

Choices.....

Cables seem to bring out more strange threads than any other audio topic I know. Audio theater of the absurd I guess. That's my experience.

First the disclaimer, I am an engineer, I design cables for AV and stereo audio systems. I have worked exotic and precious materials since the 1970's. I have the materials and the resources to make just about any cable design I care to evaluate for performance. I say this so you will understand my point of view. My personal speaker cables and interconnects are silver, most of what I manufacture is copper. Purity, crystal orientation, hardness, and surface finish effect the performance of conductors. These are just a few of the properties of conductive material considered in the design of a conductor used in a cable system designed to operate with the same performance level for an extended period of time.

I like the performance of gas/vacuum conductor suspension designs in general. That means a conductor suspended in a tube. If the tube is sealed then surface changes on the conductors can be controlled. I prefer cable designs with sealed designs over the same design which is not sealed.

In general oxidation and corrosion of conductors and terminals is not a good thing given sufficient time. In our atmosphere most conductor materials will experience changes in electrical properties related directly to the changes in surface chemistry which will occur naturally.

I can tell you that i have silver cables and the more old they get the better they sound because corrosion and oxidation do not affect their performance at all in fact the more age on them the better they sound.