@Lloydn, if the software plays more the recent cards from your collection, but the demos, turn your collection off temporary, just watch the demos for awhile, or don't keep all of your collection active - 15 to 20 at a time should be enough to enjoy.
Also you may try to use 'Random hotness' instead of 'Progressive' - All levels marked, in Settings _ Desktop _ Erotic level.
But that's true that the player for some reasons prefers to play the latest cards you've purchased. Just change the cards you want to play from time to time. Less active cards from the collection means more demos will play.