Ergo, preventing your death would be no more valuable than replacing you afterwards.

Well, here's the thing. My values and abilities today have taken 32 years to develop. I can identify several distinct stages where I was undergoing rapid change, and several where I was undergoing slower change; but nonetheless, replacing me today with an arbitrary newborn baby, a 2-year-old, 4-year-old, 8-year-old, or 16-year-old would not seem to be a one-for-one trade.

I certainly think the world would be worse off if my current 32-year-old self were replaced with my 16-year-old self. I was a bit of an asshole at 16.

(Sadly, I don't know of any way to demonstrate improvement that doesn't amount to either wealth signaling, wisdom signaling, or drama.)

I wouldn't assert that the value of a human life necessarily rises with age — equating experience with value. First, some people do squander their potential; and some people do start with more potential than others. But worse is age-related decline. The fact that people whose lives, experience, and wisdom I value are succumbing to the failure of their evolved physiological substrate is a dreadful thing. It's hard for me to read a Terry Pratchett novel today, knowing that his brain is right now literally falling apart due to Alzheimer's disease.

The average 72-year-old has less to offer the world than the average 24-year-old — precisely because of age-related decline. And that's a horrifying, disgusting fact. Preventing biological death without preventing mental decline is not a valuable outcome to me; I want people to retain their personality, their wit, their knowledge, and not just their metabolic function.

I don't think this is any kind of uncommon view around here — but longevity with intact mental function is an obvious win for preserving the value represented by human cognition.

Preventing my death would be no more valuable to who? A happier entity would be an improvement for who? Certainly not for me. Preventing the death of an already-conscious being would be more valuable to said being; probably to most other people, too - is it okay to murder someone if you're going to have a baby to replace them?

We already have a method for making new people, so preventing the deaths of those already here has higher priority, I think.

Look at all the ailments old age brings with it, from physical frailness to dementia, and the fact that people may have to spend decades in nursery homes when they'd rather be living independent lives.

I spent a year working at a service home. This was a private institution with motivated staff, a good staff-to-customer ratio and customers who were all relatively physically fit. Yet few of them really seemed happy with their circumstances. I'm pretty sure they would all have preferred to be in a better shape.

According to The Happiness Hypothesis, the five external circumstances affecting your happiness are noise, commuting, lack of control, shame and relationships. A declining physical condition reduces your control and may cause you to experience feelings of shame due to your helplessness. It also erodes your relationships as the people you know die and it gets harder to go meet the living ones, and you have less energy to make new friends.

Age-related decline is one of the biggest humanitarian catastrophes in our age.

I agree that if we're only considering the person who dies and the replacement person, that preventing someone's death and creating another person are pretty much the same, but I think the pain caused to others by someone dying is usually outweighs the happiness caused by bringing another person into existence. In any case, the costs of death to the people who are still alive need to be taken into account.