Genetic longevity has evolved.

Consider a queen bee. Her livespan is so much longer (several years) compared to the worker bee (4 weeks during spring/summer/fall, until winters end for the hibernating generation).

The Queen's task in the live of the hive is to provide an unqenchable source of high quality genetic material to grow worker bees from which in turn will provide the hive with the periolous work required to sustain the hive.

And yet still there is an end to the queen's live.

Cloning a plant from a branch by covering a branch in soil, have it grow roots and then sever the connection is a mechanism of getting a new copy of the organsism. It might be interesting to find out if that resets the clock on a multi-year plant in respect to the original individual from which the branch was taken... Consider the top of an pineapple... you can grow an entire pineapple plant including the fruit from it...)

So longevity is not the absence of aging.

There might be serveral distinct constituents to aging:

1 the accumulation of damage (wear and tear)

2 an actual genetic programmed decline of biological function

3 an update to the genetic programming of the entire organism is not feasible

1
There might be damage which can not be repaired. For example there might be toxic substances building up or there might be a limit to the complexity or plasticity of a neural network. After exceeding such a limit the function may no longer be available in the required quality (Cortanas's Rampage..., Prions, the degradation of tendons (for example: the ligaments in a humans knee degrade...)

2
There is a cycle of life which has evolved in multicellular organisms. Single cell Organisms still have a cycle while not aging:

Build up sufficient material in the cell to sustain 2 individuals
* divide into 2 individuals, such that every clone has at minimum the required parts to sustain itself
* repeat

All multicellular organisms start reproduction from a single cell. In their youth they build up to their adult forms which are reproductive. After reproduction the parent generation may or may not nurture the offspring.

The complex mechanism of growth from a single cell to adult form relies on molecular clocks: Puberty starts at a certain age, and even before that the development of the embryo requires a sequence of aging - for example the fingers of a hand develop out of a flat proto-hand because the cells between the fingers die. So autocytosis - programmed cell death - is essential to the development of an organism.

*3
Evolution works by altering the genetic programming by mutation in the offspring, putting these copies in living specimens of the next generation into the environment and just by chance the mutations prevail whose specimens did not die before reproduction.

So longevity and aging is of no concern to evolution by itself.

Those mutations which can prevail in the environment will be found at a later date - dying off means vanishing from the population.

So the question is how would not aging benefit the sustained success of a genetic conglomeration of genes in an ever changing environment ?

While you can not fundamentaly alter the programming of an adult individual organism ?

Longevity and aging are of no more concern to evolution as much as it affects the success / survival of the next generation while changing by selection as much as is required to survive.

You don't do anything for your offspring - you get the mayfly.

you feed the baby - bees.

you feed the baby and teach it - the cat which trains the kittens to catch mice

you extend on the training routine until you develop a culture which preserves survival techniques through the ages - homini

You need an ever extending life time to achieve this support to the next generation.

But from the point of self-reliance of the kids in their life there is diminshed evolutional pressure to keep the parents alive.

So longevity / absence of aging would be a fluke - if the old generation was not consuming ressources while still running an old inefficient set of genes and reproducing child generations with less adaptations than the current great-grandchildren.

So no aging would hinder the survival chances of the offspring.

Therefore longevity is selected for as long as the set of genes in the next generation is getting a benefit from the parents being still alive.

Immortality is actively negatively selected.

Aging is allowed by the diminishing effect of parental death on the survival chances of the offspring.