Great idea in theory, but there's a reason young people work such long hours: money. If a 22 year old graduates from college and works 25 hours a week, they won't have enough money to pay off their (almost certain) debt and live comfortably, much less have excess money to spend traveling and doing fun things. Young people work so hard so they can have the money to buy and do the things they want. Most just never stop working that hard in order to enjoy those things.
Working 25 hours/week would basically push "life" back a few years, meaning maybe you rent a small apartment and drive a old car until you're 35-40.
As they saying goes, young people have lots of time and no money, but older people have lots of money and no time.
Costs of stuff like rent and cars are normalized to average income levels. (Though of course with cars there is a base cost of manufacture that makes them less flexible than something like rent).
Which is to say, if everyone works 25 hours a week, rents will go down (because if they don't, you have most properties sitting empty). If instead everyone works 60 hours a week, rents go up.
Of course, economics is really complicated and rarely works out this simply. But that's the idea. It's a little silly to post here presuming that someone in Mr. Vaupel's position has somehow not thought of the fact that when you work fewer hours your nominal earnings go down. (I think this qualifies for what pg was calling Middlebrow Dismissal). It's a more reasonable response to say, well, of course he has thought of that, but I wonder what the answer is?
Sure, I'm sure he thought of that, and I'm sure prices would change since there would be less money earned and therefore less money in circulation. This would also require a change in standard of living though. My point is simply that people cannot maintain the same standard of living and work less, even if the entire world cut back hours at the same time. Less goods would be produced, so with the same demand then prices for everything would rise, or standards of living would fall.
As a 21 year old, I'd love to only work 25 hours a week. I'd just get involved with more FOSS projects and work on what I want to rather than what someone paying me wants me to do.