Good to hear your takes on this Spacey and Danny,Crg.
In my case I never buy a guitar with the intent to resale and so if it gets a few scratches or dings or becomes tarnished slightly I'm not too concerned. Yeah, I'm usually the guy with the dirtiest car in the parking lot. I clean it but it isn't a religion know what I mean? I keep my guitars clean mind you but it isn't a show piece for me. I'm not in the habit of wiping mine every time.
I put a lot of those plated fixtures on around my house. Door handles and light switch covers. Usually in less than a year they are tarnished. Bought a nice brass plated door handle a few years back and now it looks terrible and is past saving. This is probably the same technique used to plate guitar hardware or very similar. Since then I have decided to buy black or colored hardware. My guitars will just have to live with me.
In looking at this online a few guitarists are into clear laquer nail polish believe it or not. They put it on the plated hardware and it seems to offer some protection. Anything clear that comes between your hands and the plating and seals out oxygen and therefore prevents oxidation is a good thing I guess, but I'll never know because I'm not doing it ;)