That being said with 20 hours of fundamentals this year, that would have been nearly two and a half weeks with four day rehearsals only using two hours per day. (We normally only do two hours of fundamentals per day at our school during our summer band rehearsals)
We didn't use the 20 because we did have a season last year. Our band camp does have insane hours focusing on music, but personally I'm glad that part isn't regulated as the next week we start sharing kids with sports.
I get that the 8-hour rule isn't perfect, but I don't think it should be cut down. As others have said, there are programs out there you can go to that don't have that expectation. We're already held to a higher standard than anyone else with our rule counting from Monday through Sunday!