I've gotten everything to work perfectly and sound great using The Echonest, but I've noticed that whenever I recreate a new playlist based off of a Taste Profile, I hear a lot of the same songs. Currently, I'm deleting a user's playlist when they aren't using it (which I'm assuming puts slightly less load on both your servers and mine). This not only limits each user to one concurrent playlist, but it also eliminates the need for me to worry about the whole 24-hour playlist expiry thing.
Now I know that the playlist API has an amazing timestamp-based algorithm to overcome this (which seamlessly ties into the play and skip functionality), but this is all lost when the playlist gets deleted. For example, if I don't delete the playlist for a while, I get the perfect amount of variety. How can I duplicate this behavior without needing to have the same playlist open all the time.