I was in line for a B17 ride at Frederick MD, and the pilot called it a day before I reached the front of the line, big disappointment, but still memorable, just watching.
The pilot flying was a WW 2 veteran, had bombed Germany. Each landing was 3 point, and difficult to tell when the wheels touched from just hundreds of yards away. The tailwheel was lifted to save wear. He quit for the day, simply because he was tired! I talked with the pilot after he exited the B 17, and found out that he was retiring from flying the big iron, I believe he said he was in his 80's? and was quitting while he was still making good landings (I had complimented his landings).
A pilot who used good judgement for all his flying career.