Regarding storage conditions of working standard or secondary standard, the Ph. Eur. indicate the following: “A secondary standard is usually established to reduce the use of the primary standard and may be used for routine quality control purposes. A secondary standard shall exhibit the same property or properties as the primary standard to which it is traceable. It shall therefore be used for the same purpose as the primary standard”.
In my opinión, secondary of working standard should be stored in the same conditions of (primary) refefence standard.