im not an expert but i would think that autos on cards would begin to fade in direct sunlight without protection from u.v glass, like what happens to signed basketballs and jerseys in direct sunlight if they arnt protected
Do not ever open the curtains, view only ever under low wattage flouerenscent tubes or globes, handle only with cotton gloves, no admission to U/18's without accompanying adults, have carpenter & glazier install UV resistant glass panels to the Ikea cases........