Laudator Temporis Acti

Euripides, Phoenician Women 528-530 (tr. David Kovacs):

My son Eteocles, not all that attends old age is bad: the old have experience, which can speak more wisely than youth.

ὦ τέκνον, οὐχ ἅπαντα τῷ γήραι κακά,
Ἐτεόκλεες, πρόσεστιν· ἀλλ᾿ ἡμπειρία
ἔχει τι λέξαι τῶν νέων σοφώτερον.

Ovid, Metamorphoses 6.28-29 (tr. Frank Justus Miller, rev. G. P. Goold):

Old age has some things at least that are not to be despised; experience comes with riper years.

                                non omnia grandior aetas,
quae fugiamus, habet: seris venit usus ab annis.

Henry David Thoreau (1817-1862), Walden, chapter 1 ("Economy"):

Age is no better, hardly so well, qualified for an instructor as youth, for it has not profited so much as it has lost. One may almost doubt if the wisest man has learned anything of absolute value by living. Practically, the old have no very important advice to give the young, their own experience has been so partial, and their lives have been such miserable failures, for private reasons, as they must believe; and it may be that they have some faith left which belies that experience, and they are only less young than they were. I have lived some thirty years on this planet, and I have yet to hear the first syllable of valuable or even earnest advice from my seniors. They have told me nothing, and probably cannot tell me anything to the purpose.