Since you bolded my comment about rust, I should point out for the benefit of the other readers that the unibody of a 928 is steel, and like most/all post-1976 Porsches is galvanized and has some incredibly good undercoating/sealant. The majority of bolt-on body panels are aluminum (hood, doors, front fenders, and roof, IIRC). And aluminum corrodes, too, but 928s are again well-protected.
Aluminum boat tanks life span is 10 years, All aluminum frames 30 according to Honda i.e NSX. Porsche maybe 35 before it becomes brittle? If aluminum corrides or scratched that area will become a hole eventually.
