For you that missed the explanation of the idea FX000 mentioned here's a recap:
One idea is to add the number of cards on sale at one time. Maybe 3-6 cards would be a good number and have these rotate every two hours making each card stay on sale for 6 to 12 hours.
Let me try and explain how I mean using 3 rotating cards:
00:00 - card 1 comes on sale
02:00 - card 2 comes on sale
04:00 - card 3 comes on sale
06:00 - card 4 comes on sale and card 1 is removed from sale
08:00 - card 5 comes on sale and card 2 is removed from sale
10:00 - card 6 comes on sale and card 3 is removed from sale
Using this technique each card stay on sale for 6 hours and every 2 hour a new card is added as one is removed.
If Totem were to use 6 cards in rotation each card would instead be on sale for 12 hours. Something I think wound be a better solution.
Let me add that the number of cards and/or time interval could be tweaked with just as how the selection is done. All to get a perfect rotation :)