My experience is that the polyurethane foam material has limited life - typically about 10 years, but it varies with how much heat it sees, so a car with low mileage acculuation will probably get more hood pad life than a daily driver.

I replaced my original '88 190E 2.6 hood pad circa 1999. It started to disintegrate about two years ago despite only using the car during SoCal's mild winters (I store it during the summer and use my '91 MR2), but I had no idea how old it was when I bought it, and the aging process starts the moment it comes out of the mold.

About the same time I also replaced the firewall insulation, which required buying the whole metal assembly with the insulation installed. The replacement from MBNA has a woven fabric rather than the foam, and it has held up well.

I have a buddy who owned a complete '69 Camaro Z-28 2x4 cold air induction system, which has foam seals between the air cleaner and the hood. The foam disintegrated in the factory sealed plastic bag about 10 years ago!

Duke