A 25 hour work week that lasts into your eighties.
It was proposed by somebody at a new center associated with the Max Planck Society for the "biodemography of aging". "Biodemography" apparently is a sort of interdisciplinary field combining insights from medicine, biology, and demography.
I have no doubt at all about some of the biological benefits he describes, and I'd personally like to work well into old age (it is one of the perks of the sort of work I do - of course not everyone can). But to a certain extent this smacks of the Technocrats of the early 1930s - an engineer figuring he can order the economy in an ideal way. Fascinating stuff, but often very problematic.
There are good reasons for life cycle work trajectories having to do with uncertainty, credit constraints, human capital depreciation, consumption patterns, etc. I'm not saying we couldn't one day live in the way he describes. But you can't just say "this would be good for our health and we'd probably be happier, so let's do it" any more than I can just say "I'd like to be a few inches taller and twenty points lighter, so let's do it". I can maybe think about how I might do that in the future, but some changes are harder than others. The economy is a natural system just like our bodies and it is often more difficult to plan than people wish it was.