Even more important for a long time storing as upright or horizontal seems to me to unlock the shutter. As Mamiya recommend uncocked storing of lenses, this might be an issue for Hasselblad too (but I guess it by knowing Mamiya's recommendation and don't know it in detail for Hasselblad). On Mamiya lenses uncocking is simple, it looks like on Hasselblad system it's more complicated and you need a special key for camera and / or lenses. But if you store long time you might have a look on this question and get more informations about.