Comics are graded on the same forgiving-nothing scale as trading cards: a bent corner, a crease, or spine stress knocks value down fast. Long boxes designed for the job, kept upright and never overloaded, are what keep a collection intact.
Pro tip: Buy a few extra long boxes rather than cramming your whole collection into too few; a box packed to 80 percent capacity protects books far better than one packed to the brim.
Watch out: Overstuffed long boxes bow at the cardboard walls, which can crease the comics pressed against the sides.