Peeling paint

I have a 1997 Hyundai Excel Sprint three-door hatch and the paint on the rear bumper has started to roughen, crack and peel. I have seen other Excels with the same problem. My dealer tells me it's my bad luck because cheap paint was used on Excels and the bumpers were known to do this. My car has been kept garaged. If it's their fault, should Hyundai fix it, even though the warranty has expired?