Here are some hard statistics:

480 3 minute songs in a day (no sleep; 24 hour listening)
360 4 minute songs in a day (no sleep; 24 hour listening)
288 5 minute songs in a day (no sleep; 24 hour listening)
285 4 minute songs in a waking day off (5 hours sleep; 19 hour listening)
228 5 minute songs in a waking day off (5 hours sleep; 19 hour listening)
165 4 minute songs in a workday (5 hours sleep 8 hours work; 11 hour listening)
132 5 minute songs in a workday (5 hours sleep 8 hours work; 11 hour listening)
144 10 minute songs in a day (american pie is 8:52)(no sleep; 24 hour listening)
45 4 minute songs likely (3 hours of listening)
36 5 minute songs likely (3 hours of listening)

No matter how many songs you have, you are only going to be able to listen to 480 3 minute songs in a day unless you have more than one playing at a time. Most songs are probably closer to four minutes in length. And most likely, you only listen to about three hours worth of 4 minute songs a day. If you have a hundred CD's in your collection, averaging fifteen songs each, you will not listen to them all the way through in a day's time.

Basically, it does not matter how many songs you have, you will only be able to listen to a portion of them in a normal day. Your selection is vastly improved, but choosing from so many or managing them starts to limit your listening time even more.

Edit: A more robust view and links to government research here

Poll #184702 time for listening
Open to: All, detailed results viewable to: Friends, participants: 7

Do you think there could be a reasonable Internet business model built off of time for listening instead of the selection of so many songs?

I listen to music