Cartridge Shelf Life
Well, that really depends on the components.
If you make the shelf out of old cereal boxes, wet chipboard or my wife's Lasagne...then probably not too long.
A good wooden shelf is probably the best bet, but of course it does depend on the application. If you are talking about thousands of shells, then perhaps a steel racking system may be more appropriate.
Do remember of course, that regardless of your chosen shelving material, it needs to be properly fixed to a suitable wall...otherwise it was all just a waste of time.
I hope that helps to answer your question . . .