Cards aren't meant to last forever. If they are clumping badly, toss 'em and get a new deck.
Also, I don't think a Porper Clip, awesome as it is, will stop clumping. It will only help with warping and protecting the cards. If anything, the fact that the cards are squeezed together makes them clump more for a bit. I always have to spring and faro my cards a few times after keeping them in a Porper for a bit.