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As a cataloguer (I organize large amounts of data) I can tell you my opinion on this. People who use many notebooks are “browsers” or they prefer to visually see the amount of stuff they have accumulated. It may give them a sense of accomplishment, and in the beginning it will look pretty impressive I am sure. You feel very organized seeing all those nicely labeled notebooks. They may like to give a quick look over the notebooks to see their stuff. This will work fine until you have numerous notebooks, then there will be too many notebooks for a “quick” look at your notebooks. It will take you much longer to do your “browse” you have become so fond of. You will then be forced to use the search function t to find anything. The more efficient way, assuming you expect to have large amounts of data is to have 2 notebooks if needed for work and life or just one if you prefer. I always tag my notes, that’s the organization system I prefer to use. Not having tags will put you at risk of eventually (when your data is much larger) having searches that bring you way too much data to begin to sort through.