Years ago I had an older gentleman who'd had a massive stroke, and the family didn't want to have anything done. As always, the question of "how long will he go on?" came up, which is very hard to predict.
Because of the size of the stroke, and him developing brainstem herniation, I guessed about 24-48 hours.
Literally, before I'd finished THAT VERY sentence, he collapsed over to his right and the monitor went flat.
The daughter looked at me, stunned.
All I could say was "And sometimes it's sooner."