Today in the United States there are 72,000 centenarians. Worldwide, probably 450,000. If current trends continue, then by 2050 there will be more than a million in the US alone. According to the work of demographer Professor James Vaupel and his co-researchers, 50% of babies born in the US in 2007 have a life expectancy of 104 or more. Broadly the same holds for the UK, Germany, France, Italy and Canada and for Japan 50% of 2007 babies can expect to live to a staggering 107.

Understandably, there are concerns about what this means for public finances given the associated health and pension challenges. These challenges are real, and society urgently needs to address them. But it is also important to look at the wider picture of what happens when so many people live for 100 years. It is a mistake to simply equate longevity with issues of old age. Longer lives have implications for all of life, not just the end of it.

Our view is that if many people are living for longer, and are healthier for longer, then this will result in an inevitable redesign of work and life. When people live longer, the arc of their life stretches — they are not only older for longer, but also younger for longer. There is some truth in the cliché that “70 is the new 60” or “40 the new 30.” If you age more slowly over a longer time period, then you are in some sense younger for longer.

But the changes go further than that. Take, for instance, the age at which people make commitments such as buying a house, getting married, having children, or starting a career. These are all fundamental commitments that are now occurring later in life. In 1962, 50% of Americans were married by age 21. By 2014, that milestone had shifted to age 29.

While there are numerous factors behind these shifts, one factor is surely a growing realization for the young that they are going to live longer. Options are move valuable the longer they can be held. So if you believe you will live longer, then options become more valuable, and early commitment becomes less attractive. The result is that the commitments that previously characterized the advent of adulthood are now being delayed, and new patterns of behavior and a new stage of life is emerging for those in their twenties.

Longevity also pushes back the age of retirement, and not only for financial reasons. Yes, unless people are prepared to save a lot more, our calculations suggest that if you are now in your mid 40s, then you are likely to work until your early 70s; and if you are in your early 20s, there is a real chance you will need to work until your late 70s or possibly even into your 80s. But even if people are able to economically support a retirement at 65, over thirty years of potential inactivity is detrimental to cognitive and emotional vitality. Many people may simply not want to do it.

And yet that does not mean that simply extending our careers is appealing. Just lengthening that second stage of full-time work may secure the financial assets needed for a 100-year life, but such relentless work will inevitably deplete precious intangible assets such as productive skills, vitality, happiness, and friendship.

The same is true for education. It is impossible that a single shot of education, administered in childhood and early adulthood, will be able to support a sustained, 60-year career. If you factor in the projected rates of technological change, either your skills will become redundant, or your industry obsolete. That means that everyone will have at some point in their life have to make a number of major reinvestments in their skills.

It seems likely, then, that the traditional three-stage life will morph into multiple stages containing two, three, or even more different careers. Each of these stages could potentially be different. In one the focus could be on building financial success and personal achievement, in another on creating a better work/life balance, another still on exploring and understanding options more fully, or becoming an independent producer, another on making a social contribution. These stages will traverse sectors, take people to different cities, and provide a foundation for building a wide variety of skills.

Transitions between stages could be marked with sabbaticals as people find time to rest and recharge their health, re-invest in their relationships, or bolster their skills. At times, these breaks and transitions will be self-determined, at others they will be forced as existing roles, firms, or industries become obsolete.

A multi-stage life will have profound changes not just in how you manage your career, but also in your approach to life. An increasingly important skill will be your ability to deal with change and even welcome it. A three-stage life has few transitions, while a multi-stage life has many. That is why being self-aware, investing in broader networks of friends, and being open to new ideas will become even more crucial skills.

These multi-staged lives will create extraordinary variety across cohorts of people simply because there are so many ways of sequencing the stages. More stages mean more possible sequences.

With this variety will come the end of the close association of age and stage. In a three-stage life, people leave university at the same time and the same age, they tend to start their careers and family at the same age, they proceed through middle management all roughly the same time, and then move into retirement within a few years of each other. In a multi-stage life, you could be an undergraduate at 20, 40, or 60; a manager at 30, 50, or 70; and become an independent producer at any age.

When age is no longer the determining factor of stage, the work of managers and HR leaders changes. And more fundamentally, people of different generations will interact differently with one another. As those of different ages embark on shared activities, they’ll understand each other better. That raises the possibility, amongst much else, that older people will “age young” simply through the company they keep.

Current life structures, career paths, educational choices, and social norms are out of alignment with the emerging reality of longer lifespans. The three-stage life of full-time education, followed by continuous work, and then complete retirement may have worked for our parents or even grandparents, but it is not relevant today. We believe that to focus on longevity as primarily an issue of aging is to miss its full implications. Longevity is not necessarily about being older for longer. It is about living longer, being older later, and being younger longer.