Nah, it took well over a decade for my poor uncle to go, shoot it took over a decade before he was blaming us for starving him while we were eating Thanksgiving dinner..
Dementia is a thing that can sometimes be "handled" for a surprising amount of time before it really gets ugly. Having Brandon put a lid on a day every day for a week to reset sleeping schedules so he can function during a speech or a debate, things like that, as well as some drugs that can help temporarily.
He would not be dead by now. He's not yet at the point where even the early hours after waking up will see him standing in the front lawn angrily throwing poo at passersby...
It took my mother a decade, but four years in she was not performing the way Biden is, by a long shot.