i've now owned my computer for almost a full year (minus the 7 days the mac geniuses had it.) and out of the 5410 songs (46.9 days - 22.53G) i'm down to 3828 songs (10 days - 15.8 G) being unlistened to.
i think what i'm going to have to do to finish this is start moving my regular stuff off my iphone and start putting only unheard stuff on it.
i try to do this as a way to clean some stuff out, and make sure that everything in there is worth it. obviously it was a bigger deal when i had a slower, crappier computer with less memory. the macbook can handle having the extra stuff in there, but still... why not clean?