I used to have a ton of notebooks, but, as you mentioned, too many notes fit in too many notebooks. However, since reading/viewing “The Secret Weapon,” that has all changed. Everything a person thinks s/he needs in a notebook can be made into a tag instead. And tags can be nested more easily than stacks. I’m sold. I have my GTD system set up (Actions Pending and Completed), and then I have an Inbox and a Cabinet for the elephant. Everything else is tagged. Pretty simple. I’ve also recently discovered saved searches, and that simplifies things even more.