No, I think age is a natural thing, and that people would go crazy if they lived too long. It would also be more expensive and dramatically increase the population - which isn't always good.
*How long would you want to live, if you could choose your life span?
I'd probably only want to live as long as I can still walk around, and do what I normally do. Which I'd say is around the age of 70 or 80.
*Do you agree with the author that "adding years to a life doesn't necessarily make it any fuller?"
yes, I absolutely agree with that. There is only so many years you can live or you'd want to live. Spending your life in the hospital or nursery home doesn't really make it any more full than it already is. Unless you can still do your daily routines on those added years.