I'd be curious to see an "official" Penguin answer here. My impression has been that most of the Cool Box items are taking up more shelf space then they are worth. That isn't to say they aren't good, as many of them are. But rather their prime time may have come and gone already and it's time to clear that space for something else.
I've been intrigued by the higher-end items that they've offered for "Penguin Bucks" (or whatever they call the gift credits,) as opposed to an outright discount.