Jep! I can understand why GRR Martin finishes slowly(/not at all) the last ASoIaF book.
I don’t think his problem is that it’s a lot of work. Because he’s done a ton of other work in the time. I think he just doesn’t know how to finish it. That’s more of an artistic problem. And harder to solve (you can’t just convert time into results in that case).
Oh definetely! But also he has spent so much fucking time with this world and these characters, redoing stuff, having his head in those words and sentences again and again and again - “Game of Thrones” (the first book) came out in 1996, so he probably started writing it a couple of years earlier. He has spent as much time inventing and redoing and re-inventing this story for almost as long as I am old. I would run out of creativity and stamina as well.
He did plan that many books on his own, though. I guess the lesson here is be conservative with promising things?