There should be time limit for example in a case of vegetative state when it is acceptable for the family to "pull the plug". Not a law but more like a guide line. Of course it is different in every case but the family should have legal right to end the suffering. Imagine yourself waking up from a coma after 20 years since you have been 18 years old. You have lost your youth. Your friends are married, moved away, dead etc. Is is life but is healthy for the person is another thing. I think that the state nor religion should have a say in any person will not to live.
I missed this topic the first time around.
Some of what the OP states above shows how problematic this issue is.
It depends of the perspective of the person considering pulling the plug.
I would hate to think that someone would end it for me thinking that if I woke up after a 20 year coma advanced age of 38 it would be too traumatic for me to continue.
When I was that age, I hardly considered my youth lost (still don't, 12 years beyond that.
I believe if my friends from when I was a senior in high school had moved somewhere, or had gotten married, I would be able to adjust to that
I remember though, when Franks mother in law was suffering terribly.
This is not a matter to be taken without careful consideration of what the person involved would have wanted, which is why it's so important to discuss this, when you are able, with those who could be making that decision for you one day.