Maybe if it causes them to mobilize, that's an issue. More likely, though, they'll just write in his name for every election they vote in till they die.
You really believe that whenever he dies, if it's from natural causes, that the maniacs in his base will believe that? I guarantee there will be conspiracy theories about it the instant the news breaks.
Rich people can afford a level of health care that us normies aren’t able to receive. All those pricey procedures and experimental medications can keep even the most withered turd alive. His father lived to 93, so if you go by that we have ~16 years left.