I think a biological historicism or directive would be insufficient to dictate the phases in our life.

What do you mean?

I mean nurture vs nature showed neither position was sufficient for description of human life.
If it was nature then society would never meaningfully develop while full nurture throws the baby out with the bathwater. You end up getting some boomer geographic historicism like what Jared Diamond had.
I think a better historicism accounts for them both.

Isn't this what Heidegger exactly meant by saying that we are beings towards death?

Ashrama

ashrama, also spelled asrama, Sanskrit āśrama, in Hinduism, any of the four stages of life through which a Hindu ideally will pass. The stages are those of (1) the student (brahmacari), marked by chastity, devotion, and obedience to one’s teacher, (2) the householder (grihastha), requiring marriage, the begetting of children, sustaining one’s family and helping support priests and holy men, and fulfillment of duties toward gods and ancestors, (3) the forest dweller (vanaprastha), beginning after the birth of grandchildren and consisting of withdrawal from concern with material things, pursuit of solitude, and ascetic and yogic practices, and (4) the homeless renouncer (sannyasi), involving renouncing all one’s possessions to wander from place to place begging for food, concerned only with union with brahman (the Absolute). Traditionally, moksha (liberation from rebirth) should be pursued only during the last two stages of a person’s life. — Encyclopedia Britannica

Stage 1: Brahmacari (devotion to learning)

Stage 2: Grihastha (starting a family)

Stage 3: Vanaprastha (withdrawal from family, beginning one's spiritual journey)

Stage 4: Sannyasi (Spirituality in earnest)

Each of these stages probably last around 25 years, assuming a life-span of a century. Indians/Hindus had long lives and I'm talking about in vedic times! Go figure!

The whole scheme is reminscent of multi-stage rockets. Elon Musk, Richard Branson, Jeff Bezos are you guys reading this?

If we could live forever — TiredThinker

The idea is not to wish for eternal life, rather the wise move is to ask for eternal youth (neoteny). Have you seen what happens to 500 year-old Greenland sharks? Not a pretty sight to behold!

No idea who that is.

I meant eternal life and eternal health. Age experts tie the two together as the worst disease are the direct result of cellular aging.

So nobody would spend more time learning handwriting, art, math, and all the stuff we currently only get bare minimums assuming most won't be used to the highest levels ever again? Maybe date later in life since procreation isn't a short window anymore. Maybe spiritual retreat at any age. Lots of unintuitive things could happen out of order and to better degrees.

eternal life and eternal health — TiredThinker

cellular aging — TiredThinker

The aging (physical or mental) rate is not uniform. If you've had a stressful life, your body advances in age faster than someone who's the same chronological age as you but had an easier life. A manual laborer at 40 looks older than a 40 year old who works in an office. My hunch is that the key to solving the mystery of aging is to be found in this difference.

Well age research into to epigenetics has made progress giving people a biological age separate from chronological age. And some have managed to reverse their biological age in some or most cell types. And in mice models they have improved their health to youthful levels and in many cases extended their lives as a result by a good 30%.

Doesn't it remind you of the Twin Paradox?

A 40 year old waitress' biological clock moves faster than a 40 year old heiress'.