Imagine that we could alter the average human lifespan to change it to whatever we want. What would be the best thing to set it to? Would it be better to let all humans live long lives, or is human life already too long as it is? Or, does the natural human lifespan coincidentally happen to be the best length?
Answer this question from an altruistic perspective in terms of what you think would be morally best, based on whatever factors you think are ethically valuable. Here, changing the lifespan should be interpreted as changing both the total time lived and the number of healthy years. So extending the lifespan to 1000 years would mean that most people are healthy and able-bodied for about 1000 years.
This question is mainly intended as a reversal test for those who argue that making the human lifespan longer would be bad because the shortness of life gives it meaning, or something similar.