There are two types of death: the kind that comes too soon, and the kind that, though lamentable, at least feels age-appropriate. When someone young passes away, the blow is made worse by all the might-have-beens—what the deceased could have done, seen, and accomplished if only given more time. When the very old die, however, the loss—while still terrible for their loved ones—doesn’t come with that same sense of unfulfilled potential. "It was his time" is the phrase that so often applies, or, "She lived a full life."

But the definition of “a full life” is expanding, and the line dividing the two types of death is retreating. Not too long ago, a person who lived until age 70 was considered to have had a good, long run. Newspapers from the early-to-mid 20th century typically treated such deaths as wholly unexceptional. The 1910 Los Angeles Herald, for example, reported that the stage actor Louis James had “died recently at the ripe old age of 68 years.” In 1899, the Little Falls Herald noted that a woman named Mary Honohan, of Brainerd, Minnesota, “died of old age at the hospital Friday, aged 70.” A reporter at the Corpus Christi Times wrote of a Soviet diplomat in 1954: “The amazing thing about Andrei Yanuarevitch Vishinsky is that he lived so long and died a natural death at the ripe old age of 70.”

It's hard to pinpoint exactly when 70 stopped being an acceptable age for a lifetime to end. Certainly, some of it had to do with gradually lengthening life expectancies. In 1900, the average 50-year-old could expect to make it to 71; today, he or she will live more than a decade longer than that. But as the definition of a long life changes, so do ideas about what people can achieve in the years once written off as “old age.” Consider the recent death of David Bowie at 69: Fans mourned the loss of the person, but also the loss of his future output.

At other times in history, placing such weight on the creative potential of a 69-year-old would have seemed the height of folly. In 1905, for instance, Sigmund Freud wrote that those “near or over the age of 50 … are no longer educable." (He was 49 at the time.) In 1937, President Franklin Delano Roosevelt said in one of his Fireside Chats that U.S. Supreme Court justices older than 70 represented a “hardening of the judicial arteries.”

That’s not to say that notable figures who died in their late 60s went unmourned. When a physically robust George Washington succumbed suddenly at 68 to what was probably bacterial epiglottitis (and the unfortunate medical practice of bloodletting), a young nation reeled, and remembered his “well spent life,” as Major General Henry Lee famously said in Washington's eulogy.

Something similar happened when Bowie died at 69, of course—reminiscences and retrospectives on his career quickly became too numerous to count. But there was an added element. People mourned George Washington at 68 because of the great things he'd done. People mourned Bowie at 69 for that reason, certainly, but also for everything he had yet to do. Leading up to his death, he went through what critics have described as “an 18-month burst of creativity.” Just as important, he had the support of a music industry willing to bet on his continued ability to churn out cutting-edge work.

Still, outdated assumptions about the capabilities of older people remain common today. As Mark Zuckerberg famously said in 2007, “Young people are just smarter.” And in a 2014 Atlantic cover story, the physician and public intellectual Ezekiel Emmanuel said he wouldn’t personally seek aggressive treatment for disease after age 75. “By the time I reach 75, I will have lived a complete life,” he writes. “I will have pursued my life’s projects and made whatever contributions, important or not, I am going to make.”

That’s his choice to make, and although he says it shouldn’t be confused for policy advice, the implication is still clear: There is a line separating the time in your life when you can contribute and when you’re done. It’s the same line distinguishing the deaths of the young from those who “lived full lives.”

The headlines, though, are full of counterarguments to that line. Had Jimmy Carter taken the same pledge as Emmanuel, for example, he certainly wouldn’t be nearing victory over guinea worm, as he is today in his early 90s, despite a diagnosis of metastatic melanoma. And, of course, there’s Blackstar, David Bowie's most recent album, which was released shortly before his death and debuted as Billboard's top-selling album—helped, no doubt, by tragic timing, but also by the simple fact that it is very good. As life expectancies continue to change, so too will our collective ideas about death and its timing—not just for geniuses who write generation-defining anthems, but also the rest of us who still have unfinished business of our own.