To keep all those teeny, tiny LEGO pieces with the rest of their teeny, tiny LEGO pieces from their set, store them safely in a freezer bag. They are thick and sturdy enough to withstand sharp LEGO corners. If the box is in nice shape, keep it and Include the bag, with instructions in it. However, if the box is simply taking up room you don't have, ditch it, and include the instructions in the freezer bag so you can easily see which set it is, or label the bag with a permanent market.