When I receive some electronic gizmo I usually take the desiccant packs and toss them in one of my SR storage boxes. I amuse myself by thinking they are doing some good. But I wonder if this is the case -- are they useful? I can't imagine they last forever...once they absorb a certain amount of moisture they must be rendered less effective and should be replaced. How often to replace? Could they be trapping moisture? How do you control humidity of your SR storage?