A good question, which can also be rephrased as; how are modules stored..?

The module concept is based on each owner having their modules at home, perhaps in a common room with others. But regardless, they must be stored and transported without being destroyed.

Depending on how one's storage premises are arranged, whether it is in a basement with stairs, an outbuilding or in a rental room, the first step is to ensure an even temperature all year round.

Wooden modules work if they get wet, rails rust if they get wet, cables can be destroyed by pests....  There are many possibilities.