115 year old Hendrikje van Andel-Schipper gave her ‘advice’ about longevity posthumously. A tissue sample showed that Mrs van Andel-Schipper still had two stem cells active producing white blood cells, whereas most of us have lost them by the time we die. So that could be the explanation for her remarkable long life. Or it might not. We really don’t know.
Plausibility: ? Not a clue. Check back in a decade or so.