The longest film ever premiered was ‘The Longest Most Meaningless Movie in the World’, also known as ‘The Cure for Insomnia’, at 48 hours in 1970. It was British made and later heavily cut to 2 hours.

“Lawrence of Arabia” at 222 minutes. At least it is the longest “Hollywood” movie.

Artist Andy Warhol’s “Empire State” is just a camera pointed at the Empire State Building from the top of a nearby building. All that happens is lights going on and off in the windows through the day. It is 24 hours long, but has never been released commercially.

The longest movie is (appropriately) called “The Cure For Insomnia” and is 87 hours long.

http://en.wikipedia.org/wiki/The_Cure_for_Insomnia
But I don’t know if it’s ever been shown commercially.

The longest major release is a Chinese film called The Burning of the Red Lotus Temple, at 27 hours.