Cognitive abilities, energy, stamina, singular focus on something (or someone) tend to decline with age. Apart from being unenforceable, "encouraging students t

Cognitive abilities, energy, stamina, singular focus on something (or someone) tend to decline with age. Apart from being unenforceable, "encouraging students to wait until their 50s to pursue PhDs and research work" makes as much sense as encouraging people to wait until they are in their 50s to start playing sports professionally.