Do you have to complete The Mist in full every time you enter? Or does clearing it once “clear it for good”?

I just finished The Mist and for whatever reason I found it to be the toughest area yet for me. I don’t want to have to go through it again, but I wanted to go back to an area before The Mist and I’m worried I’ll have to do that all over again given I haven’t unlocked fast travel yet for the Organ area. So I wanted to know if I leave the Organ and go back through will I have to complete the entire maze in full again to get back to the Organ area? Or did me completing it once “defeat the maze” and prevent me from having to do that all over again?

Thanks