This is something that I've said many times over the last several years in quiet hours to Mrs Tif, which dovetails with your comments about her cult of personality. She was quite fond of her persona, and enjoyed that public profile, and I think it was to her ultimate detriment. Because she didn't want to put that to an end, she prolonged her tenure beyond the point at which she could've expected a replacement by anything close to a similar-minded jurist. Just how it appeared to me as an observer.Seeing a lot of rage on Twitter directed at RBG. Namely, why she didn't just retire at age 80 around the time Obama's second term started.
The question itself is valid, I suppose. According to NPR, she wanted to match or surpass John Paul Stevens' record of serving until 90.
I should also note that Mrs Tif has a t-shirt with caricatures all of the past and present lady SCOTUS justices with the phrase "The Supremes" underneath that she wears to marches and such.