[Opinions] Re: a great question
From what i understand, the reason why its so vague to begin with is because it means different things:
Period of time
How Conservative in use
How Common
I would say period of time seems the most apparent when describing it, yes. Common use, second.
In other words i concider a classic name one which may not have been consistantly popular, so much as a name dating back from 1750 to 1930's.....i think i stop at 30's because thats when i see a very new wave of names taking place....thats just me.