I avoid leather at all cost! It is the perfect breeding medium for fungus, mold. Even if kept dry it will slowly grow mold. If you want to use leather, I would flood it with an antibacterial spray that might give a measure of protection just be sure to let it dry completely. Right now I have a nice real leather shoulder case that has that moldy smell to it, it will very likely go in the burn pit in the backyard, it is a shame but I will not expose my equipment to fungus, mold.