Never Mess With Granny: Played straight an awful lot, albeit not with people who look much like little old ladies inasmuch as, well, immortality. As such, people can keep their physical fitness quite handily while accumulating a great many years of badass experience. (This is, of course, cheating – but then, no-one made them agree to those rules…)
Redoubled with such characters as Admiral Caliéne Sargas “the Worldburner”, who – while having no children for reasons that overlap heavily with those which got her her reputation, and the attributive name quoted above, vide. the Burning of Litash – is certainly old enough by now to qualify for this trope. Or, say, CEO Emeritus Gilea Cheraelar of Gilea & Co., the bank-of-banks which acts as a lender to a large number of star nations but, in the traditional Imperial manner, without recognizing that their sovereign status makes them terribly special and privileged – and as such, is someone who occasionally comes out of retirement to help her umpty-great-grandchildren bully entire sovereign governments into making good on their debts, or else.