I seen Shoah (1985) - an epic documentary (if it counts) about the story of the Holocaust that ran for 9h 26min! I have it on DVD (4 Disc Set & 184 Page Book Special Edition Box Set). It is a great addition to my collection.

It is a breathtaking harrowing experience. Even though I own it I couln't see myself watching it anytime soon. It is one of these films that you must see once in a lifetime. Kinda like Earthlings (2005)