In Thor: Ragnarok, when Hulk changes into Banner he ask Thor about Sokovia, which happened in Avengers: Age of Ultron.
From that it is clear that Hulk didn't change into Banner since Avengers 2. Why is that? In previous films it is shown that Hulk can change back within a day or after a sleep.
In the movie Hulk is staying in a room with a swimming pool. He could have changed back to Banner anytime. But didn't, why?
And he didn't seem to remember anything happened in last 2 years, I wonder why?