My thinking is 25 years. The main reason for this, at one point on time it was difficult to get a book on Amazon that was 25 years old. I can't find the researc

My thinking is 25 years. The main reason for this, at one point on time it was difficult to get a book on Amazon that was 25 years old. I can't find the research that claims this. But 25 years feels like a decent amount of time as well. Perhaps with an expensive extension for an additional 25 years. My personal opinion is the current length of the is unconstitutional.