I would sort of see this like taxes (haha) - at work I keep a running notebook for notes, conference call notes, to-do lists, conference notes, items donated for programming,etc. When one notebook (spiral on top is what I prefer because I’m left handed), I store it and start another. If I don’t go back to a notebook after a couple of years or so I might toss it. I probably go through 2 notebooks a year. Not exactly bullet journaling though and I’m guessing still you would only have a couple notebooks a year.