Lovely, something else for me to obsess over. I have got to retire so I can keep up with all the awesome ideas that come out of this place.
I stack mine in a wooden box with shelves similar to those pictured above. I keep new sheets in the cardboard sleeves for as long as I can and put them on the shelves, loose & partial sheets on top of them. My only real improvement is a piece of masonite cut to lay on top of the pile on each shelf. It adds enough weight to stop curling. I still have some of the cardboard boxes that discs used to come in. They are in the same wall cabinet as the flat sandpaper shelf. I usually lay a sanding block on top of the stack in each box. Some of the boxes are from the early 90's. Shelf above in the cabinet has steel wool & the top shelf is new scotch brite sheets.
Used sandpaper, scotch brite pieces, & steel wool is on every flat surface. I too have a hard time throwing it away.