I wrote an article here on splintertalk about it :)
It's called "$$$ Earning DEC with Reward Cards $$$ (Become gigantically rich 😁)"
You can find it here: https://www.splintertalk.io/@toheadi/usdusdusd-earning-dec-with-reward-cards-usdusdusd-become-gigantically-rich
There you'll find a link to Splinterstats, where you can see the status of all actual reward cards (and older ones if you're interested).