It seems to me that they should get burnt up when he flies at ludicrous speed. At the very least, when he is shot, the fabric should get damaged as the bullets bounce off of his body. I suppose the question of whether or not it requires dry cleaning would just be silly, though.
Did his little spacecraft from Krypton come with a lifetime supply of super-clothing? And in his size? Or did it perhaps come with bolts of super-fabric and super equipment that can cut and sew it? Was it the same outfit he got as a baby, stretching to size like some kind of super Lycra? Maybe that explains why he wears tights?
I can't be the first person to ask this question. In all seriousness, is this something comic fans have asked before? Is it something that ever had an official answer?