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.