my opinion on re-learning - there were multiple subjects that I took in college which went over same content that I had learned in High School. I actually enjoyed re-learning them because the content was presented in a different way, so it made more sense to me that it had before. It is one thing to learn something once, but when I learn some concept over and over again, I tend to discover something new about it or related to it. Even small concepts can have greater meaning to it that I did not saw at first.

I have similar experience with movies - Dark Knight - I watched it 4 times and each time I find it more fascinating because I saw new details in the movie.