Don't store your knives in leather sheaths. Better for the knife, better for the sheath, problem solved.
My concern with storing them out of the sheath would be damage to the edges. So how do you store your knives?
I use the foam filled plastic cases like pelican. I store the knives in one and the sheaths in another. You can tip them all different ways and they will not move. I will post a pic when I get home