I don't think he has them done, I actually think the story kind of got away from him and he is really struggling on how to get it back to his original vision. There is so much going on he's just going to need to kill a few people simply to extinguish some plot threads so he can draw things to a close in 2 books. He may be scared that people won't like how it finishes (heck, most long series like this have a lot of people who hate how they finish anyways).
I also think there is an element of marketing involved (scarcity or delay makes more people talk about it, which increases his probable audience). Sure, some might quit reading because of the delays, but vastly dwarfed by the number of people exposed to it in other ways.
In the end though, I think he just doesn't prioritize finishing it - at some point he just accepted that the HBO show would likely pass him up, and so there is no urgency to get it done. As long as he's still writing it, he is still relevant.