I have a soft spot for long pieces of music. Think twenty minutes and then some, like Octavarium (Dream Theater, 24 minutes sharp) or The Greatest Show On Earth (Nightwish, 24 minutes sharp). Or even music that must be listened by the whole disc, or maybe even the entire album. Six Degrees of Inner Turbulence (Dream Theater, more than 40 minutes), All The Works Of Nature Which Adorn The World (Nightwish, just over half an hour), The Theory Of Everything (Ayreon, easily an hour and a half), stuff like that.
Let's just say that I need to make time to listen to it.