Some people go grey before they're old.
the admiral was only from 17 years in the future.
besides we don't know how human longevity works.
their youth seems to flutter by just like our from all evidence, so really, I think that they don't even out/stabilize get ready for the long haul to two hundred until after their 60th birthday.
Forever Young is a fancy, most methods of immortality are a fecking curse.