How long do you have access to your "purchased" content?
I wouldn’t think it would be for very long. I “purchased” content on an XBOX 360 many years ago. Microsoft sent me a message shortly afterward stating that they no longer held the rights for the “purchased” content and I would no longer be able to view it.
As discussed in another thread regarding Sony Playstation “purchases,” one does not own digital media from such stores as much as one simply purchases the right to play them as long as the stores have the right to peddle them.
Media purchased from the Microsoft store will be viewable in the store app. But, I do not expect them to keep that app alive for very long. Some will have linked their Microsoft store purchases to their Movies Anywhere account and continued support for it will end soon I’m sure.