Dirk, have a look at the 1995 ECTC proceedings, for an excellent paper by R. 
Shook and others. From memory, a portion of this paper looked at the moisture 
absorbtion/desorbtion from components that were moved from ambient
conditions to a dry box, a number of times. If you are trying to set up a
factory policy, I think this will be of use.

Regards

Olly