As always, Sam, very nice insight and good food for thought.
Butters goes to daycare 3 times a week - sometimes 4 times and sometimes he stays overnight. He comes home and collapses. On those days, we don't do anything else because I'll end up carrying him. On his non-daycare days, it depends how he feels. Some days he's still recovering and is still tired from the day before. But I usually will take him to the dog park. If his life depended on it, he wouldn't bring the ball back, but he'll sprint after it like a bat out of hell. He'll do these sprints for about 20 minutes before he quits.
I'll admit that I've been lazy with him, using the park ball game as a way to tire him out. Tonight, I'm going to start taking him on the walks we used to go on at Harbor Island (see my photos). Unfortunately, that means he'll be getting treats/calories as he exercises because he's a terrible walker otherwise.