How to Preserve New Shiny Banana Speaker Ends?

Maybe my description does not convey the message across clearly. I'll try again, and sorry for the lack of terminology.

It doesn't sound as serious like the plugs have gone entirely black. It's still gold but there is a slight hint of discolouration towards blackish gold. There isn't any extra layer on the plugs. It's just that the gold somehow doesn't look as new as they were during the first time I've got them. I've taken for granted I didn't clean them for a single time in 5 years that may have caused them to lose the shine. This not only apply for the speaker ends but also to the speaker terminals of my old pair of speakers.

Well, I guess there is a reason why NEW is good. Or maybe I've not taken enough care to preserve the condition? I don't think I can get back the shine to the plugs as new but guess I'll have to use Progold more often on not only the speaker ends but also to all my electrical connections of my equipment.

Thanks for responses. Yes gold is an element that doesn't oxidize but I have the impression that the plugs must be metal or something, and the gold is just coated on it. Just checked on the specs of Nordost Z plugs(for the 1st time in 5 years since I first used them), and those plugs are berrylium copper, gold plated. I believe the gold has worn off slightly, revealing the copper beneath. There is just no way to preserve the gold finish from wearing off due to friction of frequent plugging/unplugging those plugs isn't it? Hmmm guess Aball's recommendation of getting some MIT cables may worth considering!