I have asked a few members of top clubs what their first impression/thought of their course was, and what their last impression/thought was.
Each one has answered differently to include things like culture, ambiance, intimacy, subtlety. But the common thread I am starting to see is this. Only the best courses have had the comment made that they are as enamored with the course now as they were the first time they played it. That in years in of membership, they are no closer to fully understanding the course than they were on day one.
In the end, a course must hold interest over the course of time. It isn't en vogue or du jour or forgotten, it's timeless. That's a 10 in my book.