First off this isn't one of those 'wouldn't you get bored?' things.
Let us imagine that everybody here will live to and only to some day within their 80th year of life and then die. That is the course before us all. What will you do with that time?
Now imagine tomorrow It's revealed that through Caloric restriction, taking NAD+ precursors, Wim Hof breathing exercises, PQQ supplements, 5 hours a week of HIT workouts, and monthly fasting to start Autophagey. You could add 20 years to that life span. Will you put in the work, and make the life changes to get those years, or does that feel like sacrificing too much and spending too much of that extra time working to get that extra time?
Now imagine in ten years they figure out a course of treatment that you need to go in for, almost like a vaccine each week against aging further. You won't get any youth back but the aging process seems to be stopping. But this process confirms a feared truth, that 128 is a hard limit. No one, no person has or ever will live beyond 128, most despite all efforts will be all used up and die at 124, and the only way to get to 128 would be a strictly regimented program of interventions started in the womb and managing metabolics and lifestyle options every day of your life. But that doesn't matter to most of us because the innovation can only grant us 120 years give or take 2-4 years. Would you take it? What would you do with your time?
I don't mean simple vague ideas like 'travel' but more like how would you measure your time out. Because underlying this question is an awareness that we have the chance to live longer than many of our ancestors did, but we've just moved milestones in life, '30 is the new 20', we start families in our late 20s not in our teens. etc. But in the midst of all that extra time living, it doesn't actually feel quite like we actually live more life. We've just changed the time signature, not the tune itself. Like the story of how a some fish expand to fill the bowl they live in, changing the bowl for something bigger never actually gives them more room.
I get the sense that we all have felt at some point we could use a day off, or a vacation... and then we get said time to ourselves and weirdly that day or week of time is behind us and it feels almost like it might as well have never existed, as it's imprint on our sense of life passing was just a flicker. So there is a part of me that wonders if our sense of time in life will expand, such that 3 years will become the new year, and we will simply have expanded the same sense of not enough time to live to fill any sized time we are given to live in.
There was a short story by Larry Niven, I believe, that involved a man in the future looking to the secret of a longer life. He was forced to search alone for many years because his obsession was not shared by the people around him. But one day he found an alien ally in his search, and in the discussions of their search the alien mentioned their parallel desire to not be limited to a tiny lifespan (i forget the actual number used) of a few thousand years... and it was a sobering realization for the man, that a lifespan that dwarfed his own would still feel like not enough. And on reflecting on it, felt that spending what life he had, seeking more of it might be wasting the time that could be better spend on getting the best value out of what he had. (now I don't really agree with all that idea but it is thought provoking)
And I know from my own experiences at times that you can live days that can feel like you packed a week of living into them, and a month can be had that is one of the best years in your life. Just like 3 years can go by with so little on note or value that it might as well have been a week. And so combining all of this thought, the question comes, given any number of years, how would we use them?