Marian Seldes has enormous staying power - from an article I found on Broadway.com:
Between 1974 and 1976, she racked up more than 900 performances in "Equus", first as the magistrate and later as the mother of the troubled boy at the heart of the play. For her more than 1,000 performance run in "Deathtrap" (as the playwright's murdered wife), Seldes landed a spot in "The Guinness Book of World Records" and to honor her, the producers elevated her name to above the title.
"Love Life. Live." Michael Bennett