again, and this may really just be sophistry but it deserves acknowledgment, I wanna zoom in on the phrase "the rest of his life"

Let me be clear: I understand the difference and I agree with you. The reality is that a transplant would probably be a lot of work and suffering and I can definitely understand opting out of it. All three of the grandparents I actually got to meet ended up doing this same math and getting the same result: sometimes life-extending care isn't worth what you have to go through to get the extension of life. I guess what I'm interested in playing with here is the language we use to abstract the reality, and how it doesn't really hold up once death is accepted. Treatment is a commitment. So is dying. Treatment will go on for the rest of his life. Without treatment, dying will go on for the rest of his life. A lot of the things we do and ways we look at things assume that dying is

1) very far off 2) to be avoided at all costs

If either of these things becomes untrue the calculus we do to determine reasonable courses of action goes flying out the window. Neither of these things is true for this person, but it's true for all (for a given value of all) of us trying to talk about it and I see throughout the thread this interesting disconnect that basically boils down to people saying "You can't kill yourself! You'll die!"