For sure keep. Inner (gun box) and outer (shipping box). Break em' down if taking up too much room,.. but save em'.
Yes, ....You need the box it came if you decide to sell it.
yes, i have every one.
Yes, must keep the box.
I keep inner and outer gun boxes as well as scope boxes.
Not everyone has the real estate to stash big cardboard boxes by the dozen. I have kept my (inner / retail) gun boxes, to ship the guns I sell in... I have no way to keep the nondescript, much bigger outer boxes...