Three rules: keep them in their ESD packaging until the moment of installation, store them in a dry room-temperature cabinet (not on top of the rack, not next to transformers), and keep the configuration memory intact by avoiding unnecessary handling. Modules do not need periodic powering in storage, but the cabinet should be frost-free and free of condensation. Label the shelf with the module type and slot it serves — a spare that takes twenty minutes to find is not a spare.
