This was discussed last night and it was pointed out that some medicine cannot be stockpiled. For example, there are radioisotopes used in some treatments and investigations with a half life of roughly 2 hours. That can't be stockpiled.

(When I was 40 or so I was investigated a potential lung issue - there was none. But the radiologist/lung specialist asked me is I had any questions about using one of these isotopes, presumably anticipating the need to settle fears. Instead I asked him how they compensated for the fact that with a half life of 2 hours it would have decayed significantly during the 1 hour investigation itself and how did they compensate for this effect? We had a really interesting chat.)