Your prime years are whatever you make them, it’s borderline depressing when people think their best years are behind them when they possibly have 6-7 more decades to live.
Then consider that in your final decade or so, your options are extremely limited because of severe mental and physical decline. 1 in 9 adults will spend one or two of their final decades in a long goodbye due to Alzheimer's alone.
But the decline starts earlier, mental speed is high until age 60. This will affect your job and career prospects, and even if it doesn't for you, employers (esp. in tech) think it will and discriminate based on age anyway (roughly ~45yo based on some articles I've read). If you're a blue collar worker, a career of hard physical labor starts to hit a wall. If you're a woman, fertility starts declining (and childbirth health risks dramatically increase) fairly early (~30) and dating desirability follows rapidly.
Those are just the terminal issues, psychologically your life path more or less calcifies as you age. There's no age cutoff but, for example, it's said that the longer you stay in corporate work, the more likely you'll stay there and the less likely you'll succeed at entrepreneurship. I'd speculate there's maybe one or two more major life pivots in a 30yo.
Most of these factors don't exactly make life unbearable, but after a fairly "young" age (around 30 I suspect) a lot of doors start closing and it only accelerates from there. Depending on what "prime" or "best" means to you in terms of life goals, realistically you have much less than 6-7 decades to exploit them. I generally disagree with this attitude of oh don't worry you have plenty of time, life is much shorter than you think.
Nevertheless, once your doors are shut, there's little use in ruminating over the missed opportunity.
My attitude is certainly not of the 'oh don't worry you have plenty of time' because we really don't have that much time. But if the view is that in an 80 or so year life span, you got to get in 8-10 golden years as a healthy American, oof, that is pretty tough, and I probably won't change that mindset.
I think chronic conditions are also hard to plan for in your head, so some preset stats-based options for medical costs could be helpful.
No one intuitively imagines it'll happen to them but something like 60% of 65yo+ adults managed 2 or more chronic conditions, which are conditions like heart disease, diabetes, strokes, and of course cancer. It's more likely than you think. Stuff like cancer won't just kill you sooner, it'll bleed you dry towards the end of your life as you attempt all manner of surgeries and treatments to delay the end.
One drawback that occurs to me about the idea of projecting lifespan/healthspan is that with the data you'd need, you get into PHI territory pretty quickly right?
[0] https://github.com/MikePiper/open-social-security/blob/maste...