There is no hard and fast definition...in real life, as opposed to what takes place on internet Rolex forums, probably very few people know or care if they're owning and wearing a Rolex that is or isn't 'vintage'.
If you must put a time to it, 30 years could be OK, and so could the models that were made with plastic crystals, but I own a 28 year old Rolex Date that came with a plastic crystal and a quickset movement that I bought new...so, is that vintage or not? You could say that when Rolex USA stops being able and willing to service a watch due to age that is the definition of vintage. You could put an arbitrary overlay that when Rolex went to 5 digit model numbers, up from 4, that that is the timeline for vintage. A few years from now I can see the so called experts saying that a Rolex with Tritium markers is vintage because of the transition to luminova.
The definition of 'vintage' can be what you want it to be...not what the forum posting leaders say it is.