I think we, as rational human beings, deserve to choose the time and manner of our deaths if outside circumstances do not cause them to occur sooner than we would like. Of course, it is important for people to also have access to help and therapy before making that decision, but in the end, if we can't control our own lives and bodies, what does freedom mean? I'm with Belk on this one. I'll be making a living will, probably when I get to be about forty, with contingencies for everything I can think of. Less than being a vegetable, I don't want to be a burden on my family, a constant source of pain and a financial black hole (medical stuff is expensive, and we are of very modest means.) I mean, if I was a veggie, I wouldn't know, would I?
It's interesting to note that my brother sees things the exact opposite way. He would never want the plug pulled, so long as he was still in some way alive. We've both agreed to honor each others wishes in this if it ever came to that.
But none of this really answers the question. The OP called for scripture about this and no one has provided any. Surely there are some relevant passages in that big ol' book that would apply?