Beagle-I will admit that the 'C's were in better condition than the 'K's but there were still issues that you would never has seen unless you were with us on the shop floor. The main problem was the age of the Aluminum used for spars and primary structure and not a fatigue problem.
Generally the frames that carried HRH would have been the freshest off a major, for obvious reasons, with all lifed items replaced at around half life (IIRC) as required, so they would be flying in the best frame available.
I would imagine that the amount of money spent on that fleet in the 10 years after I left far out weighed it's value. The hangar at Saints supposably built for the majors, the centre wing box rebuilds plus all the other work that should not have been required from a recently 'refurbished ' aircraft.