Correspondence with Graham Oppy on mathematical difference between infinite & indefinitely long lifespans; part 2

For the initial email exchange please see: Correspondence with Graham Oppy on mathematical difference between infinite & indefinitely long lifespans; part 1

Email #3, 24th of February, 2020

Hi Graham,
thanks, I’m blown away by the breadth of this argument, and the finite list assumption on strong upper bound ‘wipe-out’ events of humanity’s existence make sense. I need to think a bit more on exactly what kind of mathematical argument is this, seems familiar from analysis, some middle value kind of argument maintaining existence but not showing unicity of an opportunity, but am running ahead of myself.
However, my question is really framed with an individual human being in mind, and assumes a technology that eliminates all internal aging-related (very distal and not proxy) causes of death and assumes only non-zero chance of dying every day (every minute, every second,…) from external causes. And making a clear mathematical distinction between individual  indefinite lifespan, as opposed to potentially infinite lifespan is the question at hand.
So the granularity of the argument am looking for is different than in case of your argument, am talking about individual’s indefinite lifespan, not humanity’s total lifespan. That said, this does not mean that the 2 kinds of argument cannot meet somewhere in the middle. Yours is a top-down argument launching from humanity’s wipe-out event, mine is bottom-up, starting from and focusing on an individual human’s external wipe-out events, like an infection. Where do these 2 kinds of argument meet, at what granularity?
Cheers, Attila  

Email #4, 25th of February, 2020

Hi Attila!

There is one way pretty clear way in which the arguments meet. If there cannot be human beings when protons decay, then I will not survive proton decay.  (This argument repeats for all the choice points at which humanity might be wiped out.)

To bring this closer to home. If humanity goes extinct early in the twenty-second century as a result of runaway warming, then, no matter what, I shall not survive beyond the early part of the twenty-second century. If the coronavirus goes lethal and wipes out humanity before the end of next year, then I will not survive beyond the end of next year. Etc.

Turning the argument on its head: If I can survive the decay of blackholes, and there is no further existential threat to me, then it seems that I might survive forever. That is: it might be that, for every future moment, I am alive at that moment.