Note that this is not the situation our supposed deathists find themselves in. They are not expecting some future change in their circumstances that would render death suddenly a thing that they want. They don't want to die today because they are (for example) living comfortably in a retirement home, interacting with their children and grandchildren. There is no reason to expect those conditions to change anytime soon barring death, and in particular, there is no reason to expect those conditions to change in such a manner as to make death preferable to life.

You're kidding right? There are a great many scenarios which would make death preferable to life and we see them happening to people all around us regularly.

You're making the exact illogical claims that I was talking about.

Many elderly people, faced with a slow decline pre-commit to some Schelling fence or set of conditions for when they want to stop living. It may be when they can't remember their childrens names or similar. They know with absolute certainty that it is coming but may not want to die today.

Believe it or not "How about June? " genuinely is the kind of thing that people sometimes say about dying.

http://www.nytimes.com/2015/05/17/magazine/the-last-day-of-her-life.html?_r=0

http://slatestarcodex.com/2013/07/17/who-by-very-slow-decay/

Even without alzheimer's given enough time I can certainly see myself picking some arbitrary time to die. I'd quite like that to be far more than 100 years after my birth but lots of people have no problem imagining wanting to die eventually even without extreme or horrible events.