I also could probably rewatch Annihilation, but I probably never will rewatch Ex Machina as it's one of those movies that really blew me away and the rewatch will likely ruin my perfect memory of it since a lot of the tension that was there on the original viewing will be gone. Also, I have a massive backlog of things i still want to watch so I rarely put something on that i have already seen unless I want to show a certain movie to someone and watch along.