I keep mine capped and stored front-end down in a canvas camera bag. This makes the lenses easier to grab and use in the field, and keeps the working mechanical parts of the lenses facing up so they won't be damaged should I drop the bag. The camera bag is kept on an open shelf in my "office," which is in a pretty typical American house. It's heated and dry in the winter and dry in the summer. There's no mold on the walls, so I don't worry about the lenses. If you're worried about humidity, keep your lenses in a sealed tub with some reusable silica gel packets. Bake the packets every so often to "recharge" them.