Cato Maior de Senectute, 32

"But even granting that youth enjoys these pleasures with more zest; in the first place, they are insignificant things to enjoy, as I have said; and in the second place, such as age is not entirely without, if it does not possess them in profusion. Just as a man gets greater pleasure from Ambivius Turpio if seated in the front row at the theatre than if he was in the last, yet, after all, the man in the last row does get pleasure; so youth, because it looks at pleasures at closer quarters, perhaps enjoys itself more, yet even old age, looking at them from a distance, does enjoy itself well enough. Why, what blessings are these—that the soul, having served its time, so to speak, in the campaigns of desire and ambition, rivalry and hatred, and all the passions, should live in its own thoughts, and, as the expression goes, should dwell apart! Indeed, if it has in store any of what I may call the food of study and philosophy, nothing can be pleasanter than an old age of leisure. We were witnesses to C. Gallus—a friend of your father’s, Scipio—intent to the day of his death on mapping out the sky and land. How often did the light surprise him while still working out a problem begun during the night! How often did night find him busy on what he had begun at dawn! How he delighted in predicting for us solar and lunar eclipses long before they occurred! Or again in studies of a lighter nature, though still requiring keenness of intellect, what pleasure Nævius took in his Punic War! Plautus in his Truculentus and Pseudolus! I even saw Livius Andronicus, who, having produced a play six years before I was born—in the consulship of Cento and Tuditanus—lived till I had become a young man. Why speak of Publius Licinius Crassus’ devotion to pontifical and civil law, or of the Publius Scipio of the present time, who within these last few days has been created Pontifex Maximus? And yet I have seen all whom I have mentioned ardent in these pursuits when old men. Then there is Marcus Cethegus, whom Ennius justly called “Persuasion’s Marrow”—with what enthusiasm did we see him exert himself in oratory even when quite old! What pleasures are there is feasts, games, or mistresses comparable to pleasures such as these? And they are all tastes, too, connected with learning, which in men of sense and good education grow with their growth. It is indeed an honourable sentiment which Solon expresses in a verse which I have quoted before—that he grew old learning many a fresh lesson every day. Than that intellectual pleasure none certainly can be greater."
Cicero, Cato Maior de Senectute.