[Pseudoscience-is-malarkey (OP)]

These two stars have lived a long time, billions of years, but are not one of the immortals. They're old and sick... Dying, in fact. By the standards of our existence, they probably have long to live yet. They will probably still be pulsating when the greenest among us humans, such as Princes George and Louis, Princes Charlotte, Sasha and Malia Obama, etc., have gone to our graves. But in terms of their (the two said stars) existence... time has grown short. They will turn cannibal on possibly half of their orbiting children and then finish off the other half with a beautiful supernova. What star would you put your paycheck on that humans will witness (assuming we're still here) to go out first?

[Petrochemicals]

https://www.theguardian.com/science/2023/may/26/its-new-territory-why-is-betelgeuse-is-glowing-so-brightly-and-behaving-so-strangely

[Eternal Student]

Hi.

I don't know.   As you've indicated we only have approximate time estimates where getting the order of magnitude right is about all we're expecting.

We think various stars have gone supernova and been observed already.   See https://en.wikipedia.org/wiki/History_of_supernova_observation   for a discussion of several observed astronomical phenomena that could have been Supernova events from  about 4500 B.C.   through to 1604 AD.   Evidence and records are very unreliable for the earliest dates.    The earliest event that we're reasonably certain was a supernova was observed by Tycho Brahe in 1572.

Best Wishes.