Yea people do. Some of the more recent interviews with Jimmy Carter is a good example. Recent as in pre his wife passing away. I havn't seen any interviews of him since then, so I am not sure if he is declining. It is often that in a long marriage, when one partner dies, the others start slipping. But the ones before, he was in his upper 90s and outside of the fact that me may not move particularly fast, he was (still is?) still sharp as a whip.