My rule of thumb is that people remember things one or two layers lower than their max. If you learned calculus then you wont forget basic algebra. If you took a grad course on electromagnetism then you wont forget basic calculus. The same goes for algorithms, if you learned them once and then never had a course where you built upon those to make more advanced algorithms you will forget them. But once you start to see them as basic building blocks for other things then you wont forget.

So from this rule, if you just learned the rules for chess you would forget them. But if you started trying to win chess games and viewed the rules as building blocks for strategies, then you will remember the rules for chess. Then you start to compose strategies etc.