You couldn't get me to go travel around and sit in a hotel room again. I have no interest in doing that. So everybody's happy. I am, at 74. Some people like doing it, but I never was much for that, anyway. It's a lot of work. So the only thing I miss about all of it is the camaraderie of the tour, but that doesn't offset the rest of it.
Singing harmony is not the same as singing a part in a choral group, where you know you're going to have to hit this note and then that note. There are nuances that change every day. Maybe today you have a slight cold or voice fatigue, or you've done something and there's a slight difference in your breathing.