It's my understanding that the two main things that damage unexposed film are heat and radiation. If stocking up on film is becoming more common, then these two factors need to be taken into consideration, so that using film past the expiry date on the box does not become a worry. Protecting against heat can be achieved by storing film in a fridge or ideally a freezer. But protecting against radiation is not so straightforward. Ideally film would be stored far underground, but this is not generally possible. In addition to cold storage, should film also be stored in those lead-lined bags that are/were advertised to protect film against airport x-rays? Or would they be ineffective against the kind of background radiation that is normally present?