The Red/Blue Arrow KEM's were one of the first "nice" setups I ever bought. To this day I think they had the best feel of any brand and that includes Copag, Fournier, Dal Negro, and the like. But it didn't take more than a month of moderate use (one or two games per week) for them to warp. The red deck warped uniformly to where the center of the card bore the weight of the deck while the corners bent upward. The blue deck didn't have that problem and lived on much longer.
I think it's interesting and worth noting that you had the same experience with the Red Arrow KEM's. Between the two, I'd much rather have the Blue deck in good shape and pitch the red one, but it just doesn't feel right using a non-matching set of cards when you have 2 decks in rotation.
The Party Poker plastic cards (I think they're Fournier) were my second favorite cards in terms of feel. They lasted much longer, but unfortunately the Queen of Clubs got a crease in it and it shows very clearly in the dark green background. You can see it from across the table, so that deck had to go as well