Originally Posted by
Wrathmonk
There is more to calculating the out of service date than aircraft fatigue. Availability of "obsolete" spares for an aircraft no longer in production (for instance) [and why, when they extended the PR9 they were forced to either rob museum displays or individually craft spare bits].
Indeed it is often the inocuous bits that 'last for ever' that break. Floor panels suddenly wear out. Catches fatigue. Fasteners don't. Etc etc. All fixable but all add to the technical burden.
A silly one on the Nimrod force was light bulbs. For much of the year the aircraft flew in daylight. Come the winter and all was gloom in the cabin until litterally dozens of pea bulbs etc were changed.