The claim has been made that, all things being equal, it is better to be alive than dead. I dissent.
It is much more complicated than this. If I knew somehow that I would spend the next fifty years of my life in Guantanamo bay, I would rather kill myself than suffer that fate. If a fortune teller showed me that I would be in a car crash and lose all sensory input, but would be kept blissfully comatose on cocaine and ecstasy, I would get my affairs in order and end my own life. And yet, if I knew that every day for the next 50 years I would be horribly tortured, but my experience would eliminate suffering from everywhere else in the entire world, I would accept the fate and do my best to steel my mind for the horror that would be my life.
I want to feel like my existence has purpose. I want to make the world a better place to live in for other people. I want to be happy and experience pleasure. These, not a primordial drive to keep myself alive, are my motivations. Killing myself would be the only rational chice if I knew that my life would be worse than my death.
I'm not trying to advocate suicide. I'm simply saying that the will to live is not a basic motivating factor for most human beings. So when the argument is made against life extending technology, rather than countering it with "all things being equal," try "existence being pleasurable..." But don't claim that existence of sentient beings is inherently good.