The thought has occurred to me that we'll only retire the current fleet of 60s/70s GA aircraft after a spate of horrific in-flight break ups. Metal eventually breaks after repeated loading and I can't imagine that owners will withdraw their machines from service 'prematurely'.
Well there are plenty of metal aircraft even older than that that are still flying...I don't see any particular evidence to support the belief that once aircraft get to a certain age they are liable to start falling to bits, provided they have been well maintained and not over stressed.