known many who have retired early, then done supply teaching.
Not as physically damaging either, which is the point I was making
Having done both, I'd question the suggestion that supply teaching is less physically damaging. Coping with several different sets of children who you don't really know, day in day out is amazingly tiring and nerve-racking.
Interestingly, one of the reasons why the 'cover supervisor' role has grown recently is because schools have discovered that having people who are permanently attached to the school, are known by pupils to be on the staffing strength and tend to see classes on a more regular basis than the one-off visits made by external supply teachers is helpful for both the students and the adults involved.