One thing I haven’t seen anybody mention is how many fewer shows people went to in those days, even the hard-core show barns. There weren’t any Florida circuits (or if there were, we up north didn’t know about them 
Our showing year started in April with a couple of unrecognized or C-rated shows. In May, we started to get serious–Sugartown, St. Christopher’s, Radnor–leading up to Devon. June was busy with something every week–Upperville, Ox Ridge, Fairfield–but in July and August we showed only intermittently (my trainer thought it was too hot to show.) By September when we kids started school again, we were mostly prepping for indoors (often as not at home.) After MSG (or Toronto for some)the year was over.
The older campaigners were turned out for several months. Some of the younger ones went hunting. Others went out on trails (known in those days as “going cross-country”) Though horses were started younger than they are now and routinely jumped higher, they certainly didn’t seem to break down as often.