Sometimes I don't know where all the thoughts in my head go. For me the problem has never been having ideas, it's remembering the ideas. Even if I actually manage to write down an idea, bringing it to mind later when I need it can be less than certain. On top of that there is reference material to deal with. Even if I do manage to read the tons and tons of paper that passes over my desk, retaining that knowledge so that it's available, especially if it's not immediately useful, is difficult.