So yeah, the Flaming Lips have a done a song that's 24 hours long called "7 Skies H3." Released on Halloween 2011, the fact that the song lasts a whole day isn't the kicker, it's that if you want to own a physical version of it, it comes in the form of a usb drive in a realhuman skull. Oh, and there are only 13 of them and they cost $5,000 each.
The band has also done a six-hour long song called "6 Hour Song (Found a Star on the Ground)" they refer to as the Strobo Trip. Sean Lennon, son of John, and member of the band The Ghost of a Saber Tooth Tiger, guests on the song to read off a list of names of people who donated $100 to the Oklahoma SPCA and Academy of Contemporary Music at University of Central Oklahoma.