The word vintage certainly applies to the age of a thing, but how old something must be to be considered "vintage" depends entirely on a particular state of mind or generally accepted parameters. A teenager would probably call a bicycle from 1990 vintage without hesitation, while a senior citizen might scoff at calling something from 1975 vintage. Alternatively, different things become vintage at different ages under general criteria - a vintage phone is probably much older than a vintage bicycle, mainly given the fact that only phones which are relatively old are considered collectable simply due to their age.

As posted above, something can be considered "classic" mostly based on its qualities. In the case of bicycles and in particular among members of this forum, classic bicycles are usually built with materials and methods that give a nod (or a wink) towards vintage material.

That's my take. Cheers!

-Gregory