So he can just completely forget we exist for however long and then drop back in and it's like nothing ever happened. That seems so very wrong.
It IS wrong what they do, and its not something you or I could do. He doesn't forget you exist, however, he pushes feelings down, denies, drinks them away, escapes them however he can. He isn't happy anywhere, no matter what you think. But he will blame you for any bad mood if you give him a chance to.
Its not fair, its not right, but its what's happening. You have a good attitude about it though. There is nothing you can do to change it, so just hop off the coaster, and make your own life, until your husband can figure out what he wants/needs.