I keep every box for every gun that came with one, regardless of whether it's a serious high end gun or a cheapo "goes bang" pistol or rifle. Both plastic and cardboard. Like a few others here, I don't plan on selling anything from my collection. When I assume room temperature every gun I have will be handed down to somebody who would appreciate it. Actually, probably long before I'm completely gone. I want to do that while I can still tell the difference between a bolt rifle and a semi-auto! I'm convinced that for the higher end guns the case/ box does add a little value. Other guns, probably not so much but although they currently take a huge amount of space stacked in the second floor of my garage, especially the rifle cases, I can manage. I don't expect to get MANY more at this point.