I've known virtually no pilots who voluntarily gave up flying until at-least their 60s, but I've known quite a lot of pilots who gave up airline flying. For example (all real)...
- A civilian test pilot instructor at ETPS who left Virgin after getting fed up of flying 747s.
- A former airline captain who lives locally to me who got fed up of the airline schedule and left to become a light aircraft QFI
- A very well known test pilot at CAA who did 5 years as an airline captain until he could escape to real flying again, even if it did involve working for the CAA.
- A former military pilot who left with a CPL, did commercial flying very briefly then gravitated to (flying) missionary work.
- Most AAIB ops inspectors are ex airlines, and maintain currency but have slotted into this partly ground based (but 100% aviation) role.
- The Piper dealer in the Czech republic used to fly 737s but decided that he prefers flying, selling and supporting little aeroplanes full time. (Nice chap, also owns the pilot shop at Prague airport.)
G