Everything silver and silver plated I have ever owned has always tarnished
Yes, Ag when exposed to the air will be tarnished by sulphur (oxides) gases inside the air. Sooner or later depends how pulluted is the city airs (lots of taffics will produce tons of S02 gases).
Even sterling silvers (low purity silvers) used to made rings & ornaments tarnish, let alone high purity silvers. Pure silver should be kept away from air to prevent tarnishing.
That's the basic reason why I have to have pure silver wires stored in air-tight
flexible tubing of Teflon (again for Teflon's low dielectric loss & high wave propagation velocity).
With Teflon tubing inserted inside a heat shrink tubing (600V UL/CSA), the doube walled protective cover should give enough airtightness to the whole run of cable.
All we have to focus on is how to terminate the cable ends to the end plugs so an effective airtight termination can be made permanently.
Hint:- Silver solder to cover the entire joint so that the silver wire be 100% buried inside the solder.
Extra very short lengths of heat shrink tubings, overlapping each other, to seal up the Teflon/heat shrink tubing ends onto the connector innart with hot air gun. You'll be surprised how effective such overlapping heat shrink covers will be in airtighting the termination.
It is thinking plus handcraft.