The reason he was so economical with notes per keyword and why we too should be very selective lies in the way the slip-box is used. Because it should not be used as an archive, where we just take out what we put in, but as a system to think with, the references between the notes are much more important than the references from the index to a single note.
Use tags but sparingly by main topic. It is more important that notes are linked together, creating thoughts and new ideas, than indexed.
