I had a job in the past that was 4 tens and that was nice. Not sure I personally would want any few days with longer hours than that. Working till 70 most can probably do, but to 75 would really depend on health and the job that person does.
I THOUGHT I'd go crazy with no schedule, but everyday being Saturday is not so bad, especially as I age because I'm slowing down, and the urgency to "do something" has all but disappeared.
I DO miss the regular money as opposed to the once a month thing ... but it's all do-able.