Mike Cirba --
I'd amend your equation to say -- of golf architecture, as well as of so many other creative activities: Passion + Persistence + TALENT (sorry it doesn't start with P) = Perfection (or as close to Perfection as this Earth allows).
I would hazard a guess that golf architecture, while not one of the High Arts (right, Rich?
), is like them in this respect: Many of the practitioners hit the ground running and do their best (or, at least, most creative) work when they're young and energetic.
I'm sure it's true that some writers have one great book in them -- and only one! It may not be the first book they write, but sooner or later (even after 15 years of letting it sit in a drawer someplace) they write it; get it out of their system; and then they've said what they had to say. They may keep writing and publishing books, because it's how they make their living -- but the books that follow the great one don't quite measure up, because the writer has already said the one big thing that he NEEDED to say. (Perhaps, in this sense, they are like Mr. Crump at Pine Valley, or Mr. Jones at Augusta, or ... other examples?)
It's not every creative person who needs to be Picasso, or to try to be -- to keep aiming higher and higher; to be ever more creative, in order to stay alive. Many, I'm sure -- possibly most -- get prosperous and lazy. (Doctor Johnson: No one but a fool ever wrote for aught but money -- which clearly makes me a fool, though a more-or-less contented one.)
We could undoubtedly cite many composers and performers and artists and writers (and golf architects, and engineers, and journalists, and entrepreneurs, and corporate managers, and ... ANYONE whose work demands even a little creativity) who fit this pattern.
It may be "common sense" that people should get better at what they do, the longer they do it. But it's certainly not, in my experience, the way things always are. It takes drive and discipline (or, if you will: passion and persistence) to make it happen that way. And many talented people fall short in those departments.