I may lose my posting rights over this, but for me, the perfect day doesn't have to include 36 holes. I would be more than thrilled - in fact, it probably would be my perfect day - if I could play 18 with Greg Ramsay, Tom D and Mike Clayton at Barnbougle, and then walk the course again in the afternoon with Tom & Mike, learning about the course and what went into building it (even if it included stories about spiders and snakes...
).
I could also say the same of 18 with Mike Nuzzo and Wolf Point, 18 with Ian at Highland Links, heck, 18 just about anywhere with one of the architects on this site, or even 18 with just about any gca'er at a course he loves. I'm probably the only person on board who is looking forward to 18 with Huck at Santa Teresa someday.
One of my favorite days in golf was playing 18 at Inniscrone, then lunch there hosted by Gil, walking Applebrook with Gil and other gca'ers, and then dinner at Gil's house with the same crew, where I got to sit on Gil's deck and listen to Ran, Gil, Tom P and Pat Mucci share wonderful tales.