I found the thicker stock of Wynns and custom decks leave them more susseptable to maintaining a bend. For example, bend a piece of paper and it just flatens back out (unless you crease it) then get a piece of stiff cardboard and bend it, and it keeps its bend a lot easier. I find being gentle with them and keeping them in a shady place the best method. Also keeping dry hands to avoid weaking the cardboard is a great idea. I actually find taht washing my hands a lot before using cards shortens the life of the deck, because I'm always too impatient to fully dry my hands off properly. Water quickly warps cards, even a little bit. Dry hands is far more important than clean ones in my experiance. Might be because since I don't go playing in oil slicks, or digging up worms, my hands are usually pretty clean