Having cancer tends to negatively affect one's quality of life. ;) But it's an interesting question--quality of life vs. lifespan. Imagine if there was no possibility of prolonging human lifespan, but instead we had the means to stop aging, say in a person's mid twenties to mid thirties. Having some 50 or 60 years time with your mental and physical faculties in prime, not having to rush, being able to take your time and learn and do practically everything you want. We would live like gods.