I tend to follow the ideas suggest in the vintage and antique car market. Vintage becomes so at 25 years of age. Antique, 50 years. There are, of course, other opinions but that is my guideline after finding, restoring and riding hundreds of vintage bikes and to me, once 25 years old they are all vintage.
On the other hand, at close to 80 years old, I think of myself as an antique. And, as some might know, I go to the dump frequently, hoping to find an old, I mean vintage, road bike. Sometimes I do find something cool. Sometimes just an old but in great shape and really warm Eagles winter coat with an annoying hood...