The amount of cooling needed is not constant over time (cf. http://en.wikipedia.org/wiki/Decay_heat http://en.wikipedia.org/wiki/Decay_heat), which is one of th

The amount of cooling needed is not constant over time (cf. http://en.wikipedia.org/wiki/Decay_heat http://en.wikipedia.org/wiki/Decay_heat), which is one of the reasons passive cooling systems are designed for days rather than weeks. The first seconds/minutes are the most critical and after 72 hours the residual heat is down to a level which can be much more easily handled.