I'D LIKE TO GET SOME OPINIONS ON GALVALUME METAL ROOFING. IT'S INSTALLED WITH NAILS THROUGH RUBBER WASHERS. THESE BEING EXPOSED TO THE WEATHER ALTHOUGH THE RUBBER WASHER HAS A PROTECTIVE METAL COVER OVER IT FROM THE TOP OF THE NAIL. THE PAINT IS GUARANTEED FOR 20 YEARS BUT THERE IS NO GUARANTEE OF WARANTEE ON THE RUBBER WASHERS. I TEND TO THINK THE WHOLE SYSTEM SOUNDS GREAT EXCEPT FOR THAT. IT SEEMS TO ME THAT RUBBER WILL DETERIORATE WITH TIME. HOW MUCH TIME ARE THEY GOOD FOR? I AM LED TO BELIEVE THAT A METAL ROOF WITH HIDDEN FASTENERS IS 4 TIMES THE PRICE. ANY WISDOM?