I'm not sure anybody would make that call at her age. And to be clear, because you're trying to infer that she is older than she is by calling her "over 70", she's 7 days past her 70th birthday; I'm not sure anyone would regard that as over 70, just 70. So at what point in her mid 60s was she supposed to decide "uh oh, I'm going to die soon", exactly?
And there are so many uncertainties when a replacing a SCOTUS justice that come in to play, especially with one side who will do anything to install their totalitarian regime and the otherside is on their high horse getting their legs sliced to bits because they were too righteous to jump off for the battle - why kick that beehive before it's ACTUALLY necessary?