I’m in my 40s and 50s, and if I don’t get enough sleep, I invariably have an involuntary siesta the next day, usually by noon.
What the Goddess said. I’ve been known to pull all-nighters exclusively in my teens and in periods of extreme weather during which the general social expectation was that people would resemble zombies with better coloring.
I’m only in my 30s, but my tolerance for very little sleep seems to be fine. I’m not happy on 4 hours a night, but I work okay, and can survive a couple of days without a snooze, as long as I have access to plenty of food and caffeine. If I do it for too long I start having mood-related collapses, but that’s been true as long as I can remember, even in childhood.
What has changed is that I no longer work at all on a regular business schedule. In retrospect, I’ve always been more or less nocturnal, and never functioned very well in any structure that required me to be up before noon. It’s just that when I was younger, there were a lot more people who thought they had the authority to force me awake in the morning anyway. They could make me get dressed and shamble around, but my intelligent work has always been done between early afternoon and very early morning. Now that I’m a grown-up, I can enforce that.