> But once you understand a concept, you understand it. You don't really need to review it again. I disagree - if this were true I would still understand all o

> But once you understand a concept, you understand it. You don't really need to review it again. I disagree - if this were true I would still understand all of calculus and linear algebra, which I took years ago. I think part of what you say is true - some concepts that are understood stick with you more than the sort of fact memorization you might find in a history class. But there are still many math skills that would benefit from spaced repetition. What are line integrals used for and how do I compute one? What does the determinant of a matrix represent and how can I find it? What is Stokes' Theorem? It's one thing to understand a high level concept (e.g. an integral can be used to model continuous accrual of some quantity) versus details (e.g. how do I integrate common trig functions?).