More of us will live to 100, says longevity expert—here's how it could dramatically change our work lives

Across the world, people today are living longer. People in Spain will live for 86 years on average, slightly higher than Singapore and Switzerland's 85 years, according to a recent study. But what if we could live to 100 years?

After spending a decade researching how to live and work in the age of longevity, I found that this will be a reality for many of us — and soon, 70 will be the new 60. A long life presents many exciting possibilities: more hours to be spent, more opportunities to be grasped and more identities to be explored. Indeed, this will have major implications on how we manage our work lives.

Many of us have been raised on the traditions of a "three-stage" working life:

1. Full-time education
2. Full-time work
3. Full-time retirement

But as we live longer, it's becoming clear that a three-stage life can feel uncomfortable and no longer fit for purpose. Already, by the end of a traditional 40-year career, the skills and knowledge built at the start are substantially eroded. Imagine this erosion over a working life that spans 50 or 60 years.

Similarly, extending our current way of working could lead to a sharp deterioration of health and happiness. And imagine if retirement spans from the age of 65 to 100 -- that's a long time on the golf course. Science has even shown that without the stimulation of work, our cognitive capacities rapidly deteriorate.

What is the way forward? It appears that longer lives offer more opportunities for new stages of life to emerge and for everyone to create their own unique sequence of stages. This can be seen as a "multi-stage" life — one that truly allows us to prioritize activities such as staying healthy, maintaining friendships and learning new skills.

Right now, a "three-stage" life is still the dominant model, but some people are already experimenting and diversifying away from it: expecting to work into their 70s and 80s, they are taking mid-career sabbaticals. These social pioneers are active in three periods of life:

1. People approaching retirement age
2. People in their 40s
3. People just entering the workforce

Now in their 60s, these social pioneers are re-imagining the rest of their lives and they are looking for ways to be productive for longer. Right now, one in five Americans over the age of 65 (and one in 12 over 75) still works, and I would expect this to rise. Some are continuing in their existing jobs; others are taking on roles that involve different skills or offer a better work-life balance; some are making a productive impact on their community.

If you are in your 40s, then it might be dawning on you that you could have another 30 or more years of work. You are probably beginning to figure out how to make the most of those years. Perhaps it is time to take a "gap year" to learn new skills for a different job (a.k.a. "reskilling"). These social pioneers are questioning stereotypes of what it is to age and are reinventing this by switching and making transitions.

If you are in your 20s, then you have an array of options ahead of you. Your time horizon is extending, and with that comes many ways of thinking about your "possible self." As your life will be longer, you can extend the age range of traditional markers of full adult independence and commitment — such as getting married, having children and buying a home. And, as can be witnessed in the streets of Brooklyn, New York and London's East End, there is a chance of embracing a new form of entrepreneurship that combines work, leisure and creative space.

One thing is clear — making the most of a long and multi-stage life means taking transitions in your stride. Being flexible, acquiring new knowledge, exploring new ways of thinking, seeing the world from a different perspective, coming to terms with changes in power, letting go of old associates and building new networks. These are the transformational skills which call for a potentially huge shift in perspective and require real foresight.

Lynda Gratton is Professor of Management Practice at the London Business School. She is a fellow of the World Economic Forum and was ranked by Business Thinkers as in the top 15 thinkers in the world. Her most recent book is "The 100 Year Life: Living and Working in an Age of Longevity," co-authored with Andrew Scott. Follow her on Twitter @lyndagratton.

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