1. Mental health is a thing.
2. Even if you do have additional energy in your twenties, that's still energy I could be using on stuff other than work. Maintaining a healthy work life balance on an 80 hour week is hard work. Much better to work 40 ish and have energy to spare.
Mental health is DEFINITELY a thing, something I've been saying for several years now in a variety of contexts. "Working hard" =/= "poor mental health" though, and that's the myth.
I think "hard work" in that sense is something we should all do to experience it, even if later we choose not to live a life like that. I think there is an entire generation of people that have just sort of lost what it means to actually SACRIFICE in order to earn their salary. I think this notion that all companies have to accommodate 10,000 (or however many employees they have) different lifestyles and different attitudes is a recipe for disaster (or at the very least, poor corporate performance, and like it or not, that's all that matters if we want to continue to have a job). Companies typically end their fiscal year in December; it's not that insane to think that there may be increased activity around that time; for some, sure, go home and pound eggnog. But for all the grief that CEOs/C-Suite executives get for being paid the big bucks, they ARE taking calls and making decisions on Christmas Day.
I can remember working in the environmental industry and having to remediate a big name company's site (you've used their calculators, I'm sure). We had to remove a transformer bank, dig out the soil underneath, replace it, and the transformers, over Labor Day weekend when the plant was on shut down. We strategized it, I hired a company that had duplicate equipment just in case something broke, and we set out. It was going to be a 48 hour marathon (we had something like 56 hour window before it impacted production). A hurricane came in that morning. We persevered; the lead supervisor for my sub had a heart attack an hour into the work. We persevered; I asked the guy on the concrete truck if he knew anyone that could help frame out the footings (one of the supervisor's tasks). I ended up giving him $300 cash to do it himself. We worked for two and a half days straight, sleeping in two-hour shifts. Rather than that being a negative, to me that's a story I can tell. I'm PROUD that we had that plant back up and running on time like we said we were going to. I felt like Tom Fucking Brady (sidebar: the plant site is about five miles from where Aaron Hernandez lived).