Hi, I recently bought a type of curio cabinet to house my camera collection and I have my classic folders on display there in the open position. Is there a reason why they shouldn't be kept in the open position? They are at no point in direct sunlight, but is there anything else to worry about with the bellows when open?
In a cool, dry environment, it will not make a jot of a difference. When stored closed, the folds of the bellows are in close contact and more likely to stick or develop mildew.
They were intended to be stored folded. If your main interest in folding cameras is to use them, why not store them that way? OTOH, if the display is most important, they do look much better open. I'm basically a user and my Ikonta and Super Ikonta As , which I use when I want to travel light, stay folded in a camera bag. My snazzy-looking (albeit common) art deco Kodak Jiffy 116, which I bought for display and will never use, sits open on a mantel.
They were intended to be stored closed - and to be used on a regular basis. I agree that a used camera is best stored closed - all parts are then protected and the bellows will be opened often enough to provide ventilation to the inside. But a camera that is not going to be used (why?) might well be better stored open.