Asks Jane Brody in "A Birthday Milestone: Turning 80!" (NYT).
The article doesn't really answer the question, not any better than you'd answer it on your own: Maintain your physical and mental well being so you can continue accomplishing, and also get yourself into some line of accomplishment that's intrinsically motivating. Brody names some famous people who are still productive in their field after the age of 80 (but fails to mention Bob Dylan, who's about to turn 80).
Here's a little text from the end of the article, about regrets (which is really a different topic!):
Have I any regrets? I regret taking French instead of Spanish in high school and I keep trying to learn the latter, a far more practical language, on my own. I regret that I never learned to speed-read; whether for work or leisure, I read slowly, as if everything in print is a complex scientific text. Although I’d visited all seven continents before I turned 50, I never got to see the orangutans in their native Borneo or the gorillas in Rwanda. But I’m content now to see them up close on public television....
I thought speed-reading was a hoax. And I think it's best to leave the great apes alone. I'm put off by the elaborate fakery of traveling to Borneo/Rwanda in pursuit of an authentic encounter with orangutans/gorillas.
And is Spanish a "more practical language" than French? French is as practical to French-speaking people as Spanish is to Spanish-speaking people, I would imagine. I think she doesn't mean Spanish is a "more practical language" but that someone living in America will find it more practical to know Spanish than to know French. One reason for slow reading is that people writing in their first language are not taking the trouble to think about what they are writing.
ADDED: My line of accomplishment is blogging, and I find it continually intrinsically motivating. So though I'm only 70, let me offer some different advice about remaining active while aging. You don't have to keep powering along in the career you chose for yourself decades ago. You can discover something within or adjacent to it that is more purely what inspires you and brings you flow. Then retire and do exactly that. I called blogging a line of "accomplishment," but I'm no longer oriented toward accomplishing anything. I live in the day. A day lived now is as good as a day lived anywhere else in the string of days that is your life. What does it matter how close to the end of the line it is?
ALSO: From the Wikipedia article "Speed Reading," here's a photo captioned "Jimmy Carter and his daughter Amy participate in a speed reading course":
Do you think they are speed reading? The speed-reading craze got started with President Kennedy. Was he really speed-reading? Skim a few articles on the subject and I think you'll quickly get the main idea: People who claim to speed read are skimming. To read, you have to read all the words in order. You don't have to read. You can go way more quickly by skipping a lot of the words. But even skimming the articles on the subject, you should know you're bullshitting if you call that reading and claim to be "speed reading."
AND: Here's an article by Timothy Noah at Slate, "The 1,000-Word Dash/College-educated people who fret they read too slow should relax. Nobody reads much faster than 400 words per minute":
Studies show that people who read at or above the college level all read at about the same speed when they read for pleasure.... When you factor out the amount of time spent thinking through complex and unfamiliar concepts—a rarity when people read for pleasure—reading is an appallingly mechanical process. You look at a word or several words. This is called a “fixation,” and it takes about .25 seconds on average. You move your eye to the next word or group of words. This is called a “saccade,” and it takes up to about .1 seconds on average. After this is repeated once or twice, you pause to comprehend the phrase you just looked at. That takes roughly 0.3 to 0.5 seconds on average. Add all these fixations and saccades and comprehension pauses together and you end up with about 95 percent of all college-level readers reading between 200 and 400 words per minute, according to Keith Rayner, a psycholinguist at the University of Massachusetts Amherst. The majority of these college-level readers reads about 300 words per minute....
John F. Kennedy was said to read 1,200 words per minute. The speed-reading huckster Evelyn Wood claimed that a professor boasted of consuming more than 2,500 words per minute “with outstanding recall and comprehension.”... (Speed-reading courses teach skimming, not reading, though most won’t admit that.)...
