Most people don't really care as to how many years of life they have left. It isn't an interesting topic for them, and is thought about rarely if at all. If pushed for preferences, the average follow reverts to not wanting to rock the boat, to go with the observed defaults: to live as long as his grandparents, or just a little bit more than his peers, enough to make the point without being crass. But this is not really an expression of preference, it is simply going with the flow, the knee-jerk desire for conformity and hierarchy. Of course most people are in relatively good health and a demise by aging is still decades away, which might as well be never given the human psychology of time preference. Life is busy and it is easy to push future concerns to one side in favor of the day to distractions, needs, and pleasures.
You can conduct a survey of such views yourself. If you are reading this post, the odds are good that you have a very different view on the future of your life than do your friends and family. If you talk to healthy people you'll find that most are surprisingly indifferent to the length of time they have left before aging greatly harms and then kills them. It only becomes a pressing concern when that time remaining drops into territory that instinctively makes a person uncomfortable: a month or a year, perhaps.
One of the aspects of ancient Stoic philosophy is that length of life and even present health is of little concern when it comes to happiness. Will triumphs over circumstance, as present state of mind is under the control of anyone who strives for that goal. To quote Epictetus, the stoic can be "sick and yet happy, in peril and yet happy, dying and yet happy, in exile and happy, in disgrace and happy." In times when life was far more perilous and fraught with sickness and discomfort than is the case now, these sorts of considerations were not academic exercises.
My faltering commitment to stoicism was brought to the forefront of my mind quite recently when I read an article by Eyjolfur Emilsson entitled "On the length of a good life". The article outlines and advocates the stoic (and Epicurean) view that "a life, once happy, does not become any happier by lasting longer". That is to say: we don't need long or indefinite lives in order to be truly happy and content.
There is far more to stoicism than this small slice relating to happiness and length of life. It certainly isn't the "philosophy of what I'd do anyway," but this small slice does more or less reflect the default view of the public at large. Most people strive for happiness in the moment and ignore their future longevity, which one might argue is some mix of (a) following the example set by the norms of past behavior, (b) a response to lack of certainty and control over the future value of money and other forms of wealth, and (c) that all-too-short human time preference again.
But so what if we have a world of people who hold stoic views with respect to longevity and years of health remaining, but without any real intent of doing so. Why does this matter? It matters because defeating aging and age-related disease is a grand goal in medicine. Even if the prototype technologies might be pushed to the point of demonstration in mice for a billion dollars and ten to twenty years of work, well within the purchasing power of a large multinational research company or collaboration of billionaire philanthropists, vast resources and many hands will be needed to translate that into a full, mature, worldwide clinical industry. At this sort of scale at least a sizable minority of the population must support the goal in question for it to have a hope of moving from possibility to reality. There are many grand engineering projects and industries that might already exist in a different world but which in ours have too little public support to move forward rapidly: irrigating the Sahara, a low-cost orbital lift industry, commercial small-scale nuclear reactors, and so forth.
The near future of human longevity is not just a matter of research and building the tools needed to repair the damage of aging, but it is also, vitally, a process of convincing enough people that this is even worth doing. Anyone who has spent time looking at exactly what it means to be old, at the drawn out pain and suffering inherent in the age-related failure of all organs and bodily systems, might be forgiven for thinking that we live in a madhouse. But nonetheless, most people simply don't care about research, medicinal science, progress in clinical applications of medicine, or the future of their health, or how long they will live. These things are not important to them, and won't be until such time as they are in the clinical system asking how their pain and lost function can be assuaged - which is far too late.