On the other hand, if you look at the FRED website it shows that average annual hours worked has massively decreased in the last 50 years: https://fred.stlouisfed.org/series/AVHWPEUSA065NRUG
1951, for example, shows 2,030 hours worked on average. That's the equivalent of more than six additional weeks of full time work.
I would say that Keynes's prediction that economic growth could get to the point where we would only need to work 15 hours a week (750 hours per year, assuming 2 weeks vacation) is ... trending towards becoming true? At current trends, it will take another ~280 years.
(Obviously this is a silly prediction but, an interesting thought experiment.)