This seems intuitively true but much more generally - not just for mathematics, and not just for spaced repetition. Our understanding of fundamental principles

This seems intuitively true but much more generally - not just for mathematics, and not just for spaced repetition. Our understanding of fundamental principles in any field is deepened by exposure to them generally in different contexts. For me (as a biologist/computer science/systems design person) the quintessential examples are evolution and entropy. Both are trivial in their essence, but infinitely rich in their implications.