[quote=Pontius Navigator;2823468]There was a small matter or airworthiness and money.
Post-war aircraft were not designed to 'fail-safe' principles. That entails building in such a level of redundancy that a spar break is obvious but the aircraft can be landed safely (well that's the theory). As fail-safe was not built in an alternative safety polcy called 'safe-life' was adopted.
In safe-life the fatigue usage was calculated and each aircraft given a fatigue index. As it flew its activity was recorded on a data recorder and also by the crew. After each flight its remaining fatigue index was recalculated. Once it reached its calculated fatigue limit it would be withdrawn from service.
In the event, the Bruntingthorpe servicing, IIRC, found that the aircraft was in much better condition than expected but whether that was simply its fabric condition or its component condition I don't know.
As safe-life was a crude but safe calculation it was not unreasonable that some aircraft would have been less fatigued than expected.quote]
Couple of extra ditties here:
Aircraft are only metal and wires, so with the right attention can be kept flying for ever, in theory. Look at the B52, which is on its n-th upgrade and may well be the first aircraft to stay in service for 100 years. Not there yet but quite feasible. New wings, replaced wiring looms, new hydraulic pipes and fuel lines, new engines...lots of spares!
These were the sorts of options I believe were considered for the Vulcan fleet, too, though at this range downwind my memory might not be quite on spec.
Secondly, fatigue is only one element of lifing; simple age is another, leading to wear-out and corrosion, which also have to be factored in to maintenence and inspections.
Finally, if I recall my aircraft design lectures at uni properly, the Vulcan wing was one of the strongest and most redundant structures ever put into an aircraft. Oddly, quite unlike the Canberra which was a mono-spar design!