Air is the best dielectric. I use pure silver solid core DIY cables with no terminations what so ever. I have used them for over a year now. There is no oxidation that I can see with my eyes under the teflon. The ends will show a slight discoloration..it hasn't effected the sound from my observations.I live in the humid climate of the south as well. Once the oxygen is used up between the wire and the teflon..there's not much oxidation going on. Some audiophiles use speaker cables only surrounded by cotton tubing. If I were you, I really wouldn't worry about it. Audiophiles can get a bit carried away with this stuff some times. :-)