What about working as a CFI after airline retirement? I think teaching aspiring pilots to fly would be rewarding. And you can basically decide how much you want to work. A buddy of mine did Seaplane Ratings in his personal 1959 Tri-Pacer, and he did that while still flying for a major airline.

A number of retired pilots found out the fractional lifestyle isn't for them with the occasional 14+ hour days and all the additional duties mentioned above. If I could justify the expense of my own plane I'd love to do the "Pilot's for Paws" thing