I have a high mileage Ithaca/SKB Model 700 Trap that I bought new in 1968. It has seen many, many thousands of rounds down its barrels. Yes, I've replaced some parts but, those parts were and remain readily available from SKB in Omaha. I do keep a few parts on hand (hammer springs, etc.) but, have not needed them in recent years. BTW, despite its age and high usage, the gun still locks up tight with no play. FWIW, SKB in Omaha offers a tune-up service with replacement of wear parts.
IMO, the Japanese made SKBs are built to last several lifetimes.
DF
Montani Semper Liberi