I'm not sure where the other poster was going with the pseudo-babble...In particular he lost me when mentioning an unreferenced article about homes being built post war that had life spans of 35 years. I guess when I look around I don't see these tracts falling down...some 50 years later.
For an example of response that cites studies, including those of the USN, boatbuilders, and others with skin in the game, please read:
http://www.ericgreeneassociates.com/..._Longevity.pdf
With respect to your question, the easiest answer comes from something which is also the simplest to grasp:
How many 30 year old fiberglass boats are being retired because of problems with their hulls? That's right, none at all. Rigging, electrical, plumbing, wood treatments, layout, etc. determines that the old clunker is ready to be cut up and thrown in a dumpster.