Well, I will be the first to admit that I do not listen to it all every day. Most of my day to day use is with a randomized playlist of a few thousand favorite tracks. I could function in 20GB if I really had to. (I do this on my Karma, but it irks me.)

But I have a rather large CD library and a lot of audiobooks that I downloaded from subscription sites. I also tend to use rather high variable bitrates for my audio. It fills rather quickly...