I can only tell you what the recommendation is from one US certified AAS analytical standard
manufacturer.
If possible reconstitution should be delayed until the day of testing.
Otherwise the product/s should remain in a their respective vials in a refrigerator OR freezer . The latter is preferred if use is delayed more than 30 days.
For optimal reproducibility the a shelf life of SEVEN days may be anticipated for a refrigerated reconstituted product, while
180 days is a reasonable estimate for a frozen unreconstitued product.
However the purchasing lab should perform HPLC, LS/MS standardization testing to establish that labs quantitative baseline.
The latter SHOULD then be used for comparison to determine the effects of storage related oxidation over time, and whether the products continue to qualify for that research being conducted
The latter is at the discretion
of each .
Understand these guys manufacture AAS STANDARDS,
so the purity is of utmost imoirstabce, so the objective is somewhat different.
Finally I can tell you most Pharma lists a shelf life of somewhere bt 6-12 mos, which decreases to around 30-60 days once the vials is punctured.
The latter is based upon sterility rather than quantitative concerns.
Jim