Yesterday I finished watching Bela Tarr's 7 hour film Satantango (it took 2 days), and it's a great achievement. I will write a long essay on it over the next few days, but it really changes the perspective one has on time. Like the poetry of Walt Whitman, there are some demonstrably bad features to it, and some self-indulgence; but, like the Good Gray Poet, if one shortened the scenes, one would lose pacing, character development (yes, even in the excess there is a purpose- see the scenes with the obese drunken Doctor or psychotic little girl), and some other positives. Thus, while a shorter version would gain some, it would also lose some, but it would, essentially be a different film.
Here is a video of the great opening sequence. The music choices in this film are marvelous, and, despite this being a realistic drama, one can see the influence of horror films, from the silents through the Universal films of the 30s through the Hammer films of the 60s and 70s in this one sequence.
That all said, the one thing this film is NOT, is an epic, for it is a highly intimate and cozy little seven hour marathon.