There's longer songs than that.
Jeff Wayne's War of the Worlds: 1 hour 30 minutes. Often split to seperate tracks but it's consistent enough to be one continious song.
Several of Dream Theater's songs are over an hour long.
Klaus Shzule released tracks that lasted from 1-2 hours.
Last but not least...
Bull of Heaven's "The Chosen Priest and Apostle of Infinite Space" was... 2 months long. It's mostly effects slowed down and general ambience, though.