Old Phart, almost all metals will oxidise very slowly over time, with the exception of Gold, it brings the molecules into a lower energy state. By plugging and unplugging you rub away a minute layer of tarnish although you do expose the contact surfaces briefly to fresh air. If you leave the interconnects connected and never move them a layer of corrosion will build between the two metals and slowly degrade the conductivity. This is in part due to differing metals contacting and having different electochemical covalency. This means that when different metals are in contact with each other, depending on which has the higher covalency corrosion will flow into the contact points. This is why plumbers always keep steel pipes away from copper ones. If both your interconnects are gold plated you're fine, otherwise it is sensible to plug and unplug from time to time.
Very well sealed cables may last decades but slowly the air will get in. As much as we try and avoid it, we usually fail to stop nature corroding all around us.