i dont really have a problem with long movies. 2-3 hour movies dont really bother me, but i havent went to a lot of 3+ hour movies. most of them average 2 to 2 1/2 hours long.
that being said, this past weekend our local movie theater did a replay of the orignal lotr trilogy but with the extended versions. so each movie was roughly 4 hours long. granted there was about a 45 min break in between movies, a short 10 min break halfway thru those movies i could have justified.