This week's Parsha (Vaera 7:7) records that Moshe was eighty years old and that Aharon was eighty-three years of age when they began to negotiate with Paroh. Sforno comments that the Torah notes the ages of Moshe and Aharon to teach that despite their advanced age they made the effort to carry out Hashem's will. (The Sforno notes that even during those times, someone in his eighties was considered to be aged.) His proof is the fact that Moshe himself is recorded as explicitly stating that at eighty years of age one is indeed old (Tehillim 90:10).
This attitude of pushing oneself to be active and productive in old age has always been characteristic of great Jewish leaders. The Chafetz Chaim pushed himself to travel and motivate Jews to come closer to Hashem, even when the Chafetz Chaim was well into his nineties. Rav Efraim Greenblatt relates his experience of driving Rav Moshe Feinstein from wedding to wedding deep into the night when Rav Moshe was well into his eighties. Despite the difficulties that this posed for Rav Moshe, he pushed himself to make his Talmidim joyful at their weddings.
I was privileged to be one of Rav Soloveitchik's assistants when he was past eighty and ailing. It was amazing to witness how the Rav pushed himself to be productive despite his advanced age and poor health. After supervising the preparation and publication of the two volumes of "Shiurim L'Zecher Aba Mori Zal," he remarked to me with a charming smile, "I think I did a pretty good job." Moreover, I noticed that the Rav kept his overcoat on during the flights from New York to Boston. I later learned that the reason for this was that The Rav traveled on the Eastern shuttle on which the passengers were mostly business people. The Rav reasoned that since the business people were most likely in a great hurry to get to appointments, he did not want to inconvenience them by making them having to wait the minute or so that it would take for The Rav to be assisted with putting on his coat when the passengers were disembarking from the plane. Therefore, The Rav chose to keep his coat on during the flight and be uncomfortable, rather than disturb his fellow travelers.
Great people like Rav Soloveitchik realize that Hashem placed us in this world to be productive and accomplish great things. They seek to use every second in this world wisely and productively. Old age from a Torah perspective is not a time to spend on a golf course or playing bridge. Rav Soloveitchik (in a public shiur delivered at Yeshiva University in 1981) recalled that in Europe people in their eighties and nineties would come to the Beit Midrash and study for a few hours. He noted that this also served the purpose of enhancing the self-esteem of the older individuals. May Hashem bless us with health and wisdom to use our time wisely and productively throughout our lives.