I can't speak for every dev in the world, but I can tell you that the 8-12 hour day you mentioned is pretty much what's going on for devs under the X-Aviation umbrella. I would assume there's a number of the same from other stores.
I'll just add that I found the v10 to v11 transition to be quite a bit less cumbersome. PBR was the biggest hurdle for most of us, but that was manageable. OBJ lighting changes was another.
v12 seems to be incredibly more involved, but I do believe that to also be due to things @daemotron outlined. Devs are getting more and more comfortable writing plugins and pushing boundaries. It's great, but when we have major version changes like v12, it's a heck of an effort to get things functioning properly. I don't think a lot of customers realize this, and I know Laminar didn't help that cause when they tried to sell v12 as having backwards compatibility for v11 stuff.