The term "Vintage" can be very subjective. "Vintage" has a distinction of rarity or desirability, as well as age.
There are those in Airstream circles that consider "Vintage" as being any Airstream pre-1969 or pre-Beatrice; followed by the Beatrice 70's and 80's trailers, and then Thor Industries. The slide out versions of the 2000's maybe considered Vintage even before a regular trailer of the same year, or era.
As far as motorhomes go, there are only three categories; Argosy class moho's 74-78, 20'-28', Classic & Excella (aluminum) moho's, 78-93, 28'-37', and the final Classic's 93-96, 36'..........everything else, (fibreglass, or Interstate) may never be considered "Vintage", even though the very first fibreglass Land Yacht was built in 1989.
The only exception to this could be the B-series Airstream camper, 89-96, based on a 460 powered Ford Econoline, which may be considered "Vintage" one day, as its numbers were very limited.
Again, this is subjective and depends on which model you own.
Cheers
Sidekick Tony