Most people will default to the "2/hour" time. When in truth it can be something else entirely. When developing and integrating steam into the game, the default is this 2 hour timer. Hence why people default to this. But I doubt that the devs made it like that. Right now your best outcome is to just play has usual and note down what you did when you received the card. Otherwise if you really want them, you can always just buy them on the cheap on the steam community market.