Storing your discs in this way greatly improves your efficiency. An orderly shop not only looks nice it helps to keep you focussed on making things instead of scrounging for needed tools and materials.
The box is big enough so it won't get lost in your shop(unlike the flat packs that the discs come in) which saves time.
It's also very easy to tell at a glance if you need to buy more discs (nothing like finding out you have to go to the store to finish sanding something).
It easily stores more than 10 discs on each shelf.
It is a great way to keep your discs stored while in the shop and you can easily transport it to a jobsite if required.
It's easily customizable if desired and can be made from shop scraps.
It's also a nice beginner project that new woodworkers can do.
You can scale this box up and store saw blades in the same way (just put an appropriately sized peg in the center of the shelf and store one blade per shelf).
If your shop is set up you could probably put one together in less than an hour.
I haven't given many dimensions because they depend on what size discs you use. I have a Bosch 5" random orbital sander, so your mileage may vary.
This is the first one I made about a year ago. It's got 5 shelves (60, 80, 100, 150, and 220 Grit). I added another shelf for the new box.
This design will work for any type of sanding disc (5 hole, 8 hole, etc.) that has holes.