A 1960 Corvette is a classic...a Ford Pinto, not.

For "vintage" though I think the word has evolved to just being a fancier way of saying "old". When I was a kid, there was no Internet--if you wanted to sell something, you either posted an ad on the bulletin board at a store, or you paid for a classified ad in the newspaper. The classifieds charged per character, so ads were usually kept short and sweet: "74 Nova, low miles, loaded, 867-5309" No "vintage" description, the word seldom showed up in ads.

Then a couple of things happened. Antiques suddenly became very popular, and the Internet meant ads were free with plenty of space available for descriptions. Shows like the Antiques Roadshow began hyping the perceived value of old junk, and that filtered into classified ads. Whereas originally the word vintage also carried a slight air of being of value, now it became a fancy way of saying "old". So pre-Internet, if you were trying to sell an old piece of furniture, you would write "old table, slightly worn, cheap". Now with unlimited space for hyperbole, then the ad became "vintage table, exquisite character and desirable patina, $500"

I also see "vintage" being applied to anything more than a few years old.