I just bought a new Kallax (I now have three large ones) and I'm currently in the process of re-arranging all of my books. However, I started thinking about when I eventually get some new books that fit in (chronologically) older runs of books on the shelves, how am I going to fit them in? Move everything over? (which would take a lot of time), leave some empty space for books that may come out in the future? (which will look messy and weird) or some other way?
How do you guys go about this problem?