But the answer is different for each book. I guess the ones I look in least are the past year books, as I'm still adding to the other specific topic books, but still I sometimes search in them for something. Anyway, they're like gold for me, like the diary I kept 1992-recently – without it I wouldn't have a clue what I was doing or thinking in a particular year. They only increase in value, the longer you don't look in them!
I've been into so many different things, and am only capable of 1 or 2 at a time, so I cycle back to them (a)periodically. Before I had to rely on my memory. (I do have a filing cabinet full of photocopied books and academic papers that I very rarely look into) I did always keep a paper diary, but I didn't put the kind of stuff that would go in notebooks in there.
In the front of each book is a short contents with just chapter names, then detailed contents (thanks to shorttoc package), everything clickable. Or sometimes scrolling through looking at the pictures is faster. So, I can find stuff very quickly.
One final question, what is the difference between your 2020 book and the books which detail what you were into that year? Is a year book just a copy and paste of what you were into in a chronological order for that year? Thanks so much!
Hmm looking in my 2020 book, the chapters are January, February etc, plus To do\Done, Books/papers read, talks watched, Subjects/Projects, Writing, Dreams, Quotes, Software.
It did take me about 3 months to master LaTeX and the common packages enough that I don't have to give it a thought these days.
Before that, I spent 25 years filling notebooks with ideas, notes, diagrams, drawings, maths, etc and never looking in them again, because there was no way of organizing them. Everything was just lost and forgotten.