What if you could travel back to an age of your choosing? (Who hasn't wished for this before?) When you get there, you don't re-live your life as it has already played out; the person that you are now gets to travel backward bringing your knowledge and experience with you, though it'll be some year in the past. You can't use your knowledge of events to make a bundle of money or become a famous psychic, but you do get to live the rest of your life in a younger body, and in the earlier time in which you enjoyed it.
Here's the catch: however many years you go back are taken off of your total life span. If you would otherwise have lived to be 80, and you travel back from 40 to 20, you will now only live to be 60. The total duration of your life will not change, and remains a mystery.
Here's another catch. If you had children at the age of 30, and you travel back to age 20 while having fewer than 10 years left to live, you'll never see them again.
So are you happy with how you did things in the past? Happy enough that you wouldn't bother with a do-over, or a chance to live in your younger body? Or do you yearn enough for youth that you'd forego seeing an older age?
Your current age will probably have a lot to do with your answer. If you're 90, you may very well want to live out your remaining time in your much younger body. If you're 75, and you've been healthy and active, you may choose to try to avoid the years of declining health that may lay ahead. If you're 15, you'd probably turn down the offer and want to just get on with it. But if you're 45 (like I am), you may just want to keep on going, or maybe not ...
The scenario gets at which you value more: youth, or the full experience of your natural life. Would you trade some of the former for more of the latter?
I'm willing to bet that while we live in a society where it seems that everybody values youth, and fantasies about travelling back to a younger age seem common, most people wouldn't bother. It seems to me that for most of us, the natural journey of life is, in fact, more valuable than the ever exalted years of youth.
What would you do?