I decided years ago that adolescence in the United States ends at 32. Maybe 33. Thirty years from now, will the tipping point have ratcheted up to 50? It could happen.

For starters, parents’ increasing longevity may take a further toll on children’s maturation, as with those male apes that don’t develop fully masculine features as long as more senior males dominate the pack. Keep the elderly fit, and the edgy but dependent 18-year-old may become the edgy but dependent 48-year-old still waxing his mohawk. It’s already happening in Italy with le mammone, the grown sons who never, EVER leave home (though they sometimes rent studio apartments for entertaining girlfriends). Either the parents’ hyperactivity keeps the figli from growing up, or the sons sacrifice their chance at self-sufficiency to keep mama or papa happy. Or, in light of the plunging birthrate, maybe long-suffering single children have to absorb parenting meant for six.

But the future length of adolescence also depends on what happens to childhood. Contemporary childhood pressures children intensely but seems to do little to make them feel ready for adulthood. No wonder adolescence protracts. Jerome Kagan, the Harvard University childhood researcher, has brilliantly suggested that the reason we must continually reassure our kids with love is that they’re so useless for so long. For comparison, think about the indigenous four- or five-year-olds on a South Seas island capable of harvesting more protein for the family diet—by diving for crustaceans—than their parents can. These kids know their worth because they are contributing in a substantial way. They know how to become adults because they have spent childhood observing and excelling at the relevant skills. Dive into water. Retrieve clam. Repeat.

In the United States, the industrial revolution gradually split labor from home life. With more adult work in the office (and in the mind) and less in the home, kids stopped being able to closely observe their parents in order to learn about their own route. The 20th century invented unending school as an alternative way to prepare them for their increasingly complex and abstract future labor. As one of our sons put it, "Remind me how calculus will help me cope later."

Meanwhile, psychologists defined childhood in the family as an idealized time of love and "development." But what constitutes the right love? Or the best development? Perplexed parents have responded to these nebulous questions by providing ever more tutors, soccer skills camps, and ballet lessons. They exhaust themselves carpooling kids ad nauseam and then try to convey love by cheering from the sidelines. Meanwhile, overpacked schedules and the focus on academic achievement guarantee that children have no opportunity to make real contributions to family survival or well-being. Most do no productive work. Instead, they endure a parasitism that is at once too driven, too deprived, and too indulged. No wonder they spend every free second in some virtual world—computer or television screens before them, iPods in their ears. If this trend continues, in 30 years adolescence may become an endpoint life goal for the lucky centenarian.

Janna Malamud Smith is a clinical social worker in private practice and teaches psychotherapy at Cambridge Health Alliance in Cambridge, Mass. She is the author of three books, including My Father Is a Book: A Memoir of Bernard Malamud, which will be published in March.