I'm surprised that the length of the song has come up as much as it already has, and that so far here seems to be a unanimous preference for relatively short songs. I have about fifty songs in my iTunes playlist that are over 10 minutes long.
I suppose, like most others, I listen to music for "fun"... but I think my idea of fun is slightly different than most people I know, and "fun" is really not the word I'd use to best describe it. My need for music runs very deep, to the point that I really can't imagine not listening to music everyday. My tastes are chiefly geared toward rock, although I'm fairly open. I generally like music that stimulates me intellectually-- progressive rock, for example: Pink Floyd, Tool, Porcupine Tree, The Mars Volta. That explains all the 10-minute songs. As an artist, I also like to put on music that will play for a while as I produce my work, because it facilitates the creative process. It's hard for me to work without it. I particularly like jams, because I enjoy being able to get into a state of complete immersion in the music. Basically, so long as I find some sort of intelligence or artistic significance in a particular piece of music, I'll listen to it.