Daily Mix not really daily

[Uscore]

Whenever I open a "Daily Mix" I get a new playlist.  If I close it, and then go back to it, I get a new list of songs.

Is this expected behaviour?   It's not really a daily mix if it's a new playlist every time I look at it is it?  

Is it something like the genre of each Daily Mix is calculated once per day, and then each time you open a Mix, it makes a random playlist based on that genre?

[Uscore]

no-one?