Patrick:
There is no question that your list of "outside influences" does have an effect on one's designs. I can confirm that events such as having a son, getting divorced, and falling in love again all have a profound effect on one's psyche and one's art.
For some, too, changes in design style come from travel experiences, although most of mine came before I got to build a course on my own. The only change I can think of is that my attention to building beautiful bunkers went up significantly after my first trip to Australia, just after we'd built most of High Pointe, and you can see that influence in my courses to this day.
However, Ran has left out that at some point, the influence of the client and of the property make their presence felt, independently of personal growth. Dr. MacKenzie went from building tons of bunkers at Cypress Point and Pasatiempo to building very few at The Jockey Club and Augusta and Bayside. Was that the impact of Bob Jones? Of the Depression? Or simply of going to work on three sites with poor soils and no sand handy?
Phelps: I'm in Scotland instead of at home so I can't double-check my sources on MacKenzie's time at Crystal Downs. I'm a little surprised at the 1932 date for a second visit by the Doctor, if only because he didn't mention any of those great holes when writing The Spirit of St. Andrews.