Hmm, I'm failing to see why you would want to Premium your cards. I can see that it does reduce your CP a bit, but you can only use them once! I just got to level 10 (the 10th level of the castle, I'm at experience level 45 or so), and I don't have a bunch of cards. If I premium them all, then I can only use them once. An elixer would bring them but I only have 1 of those. The moogles aren't being very generous with their card distribution.
Really, I can't see much use in Premiuming your cards. If you have have 100 cards, then who cares if you use them all. But if you only have 20 good ones.....
