As I'm sure many have, I decided to go back to this after watching the premium video this weekend.
In doing so, I picked up a save I already had, which I had played for a while, already going through, and completing three or four 18-hole courses.
During the stream, Ryan mentioned that there's no end game to SimGolf, and I kind of found out by accident today since I went back to a save that I had already put a bunch of time into, that there actually is in fact an end to SimGolf.
(I guess what I say below could technically be considered spoilers? I don't know... There's not much to it)
When you get to the year 2046, in your end of year report, you get a message saying that you've had a great career, and you're going to be retiring at the end of 2050.
So, when you get to the end of 2050, you see...
So, yeah. Super exciting. Selecting to continue in Sandbox gives you unlimited money, and unlimited access to all of the remaining locations for your golf course. A little disappointing, but there is an end.