When the earth will become uninhabitable or humans simply cannot survive for one reason or another is not a popular topic. It renders meaningless the concepts of gods and prayers to these gods. Yet, we know from the life of other stars the life of the sun is finite. The sun is not renewable.
I think it is useful to discuss the finite nature of human existence because by doing so we have to face reality. To pretend otherwise is not reality and leads to us to fantasize about gods and other phony escapes. Recently, a scientist tried to quantify the end of human existence.
His approach is different than what I would attempt. I think there is a fair amount of information about species which are now extinct and those which have lasted for extraordinarily long periods of time. By looking at those with characteristics most approaching those of humans we might learn about our future.
Besides natural climatic forces wiping out species including humans, we all know others things can go wrong. I’ve read there is an eerie decrease in the sperm count of men. I don’t know much about it, but of course if something went wrong with reproduction it’s game over. The same with some new disease or with an inability to grow crops.
The finality of humans is not a pleasant topic but and is quite abstract. It is not as abstract and removed from reality, however, as the discussion of invisible gods.