Actually, it's quite easy from a pragmatist's point of view: vintage = obsolete. So, there's no magic age involved.
It's the marketing weenies who've obfuscated things so much. They know if they spin the presentation properly, they can charge more. If it weren't for them convincing the kids that their low-quality poorly-implemented barely functional ancient design hardware is "better" somehow, nobody would buy the crap.
Of course, there's also the flip side of the coin: if people didn't ask for junk and pay top dollar to get it, nobody would make it.