— especially if they're technical you don't use them regularly at work?
For example, I don't work in finance (got the degree but my grades were abysmal), but I have a great deal of interest in the field, so I bought the CFA and CAIA curriculum. As I read it I grasp it and answer provided problems with no difficulty. But when I return to the material a few months later, I may as well re-read the whole thing for the amount of detail I've retained.
By rewriting the material, you are recoding it. You are forcing yourself to think about the information differently: what you are doing is explaining it to yourself. This to me is far more effective than something like highlighting, because in rewriting that material, you are also clarifying your understanding.