I think Supreme Court justices should be appointed to a single 20-year term so that they will not cling to positions until the political party they favor is in power. This would take a constitutional amendment.
She's clearly trying to hold out until after the election.
But... that's playing politics for a supposed A-political Justice. If she's going to play to her brand of politics, the safer time to retire would have been a few years back under Obama. Now it's pretty iffy... and the prospect of 4.5-5 more years is probably starting to become daunting. She would be around 92 then, and have fought multiple cancer battles.
At a certain point, we've got to wonder about her actual capacity to fulfill her duties as a Justice. I have no first-hand experience with Chemo... but that's gotta be really rough at her age, setting aside everything else she's supposed to do while on the bench.