There is a cut off point where the mortar will freeze and he can't work. Not sure what that is but he's usually working most of the winter.
The GTG's are sure fun. We've been to Dennis' twice. That weekend doesn't work well with my schedule. We are planning on going to Scotty's GTG in June and see that part of the country.
Have you found anything? This is a great place to stay... https://www.thestonehouseinn.net/ We stayed there both times when we came to the GTG. Molly stayed there in '19.