I think the bottom line is that a year after you "ace" a <3 month course you can't be caught because you can't be expected to remember all that much. You may be more suspect; but there are also plenty of innocent suspects.
A hierarchy of classes that truly builds works, but they are rare. Really, we need spaced repetition for as long as necessary to master the material, not a virtual version of a broken semester design. Then there is no point in cheating.