because it’s about the time that it takes for a human to go from education to their most productive age - plus a bit for their best work to gain some traction
it’s one reason why I talk of the last lost 4 decades.
And again - this is why AI is such a game changer
AI - as it grows up in the next 10 years (ref Bill Gates). will drop this 40 years - to 6 months
so in 6 months - we’ll be ahead by 40 years in the old scale
