Beyond-use date
A beyond-use date is the point after which a prepared or opened container should no longer be used — a different thing from an expiry date.
An expiry date applies to a product as manufactured, sealed and stored as intended. A beyond-use date applies once that container has been opened or a preparation has been made from it, and it is generally much shorter.
Published beyond-use dating comes from standards that take specific inputs: a classified environment, a documented process, and in some cases sterility testing. Remove those inputs and the standard produces no figure at all — not a longer one and not a shorter one.
What it is not
A beyond-use date is not an expiry date, and a figure quoted for one setting does not transfer to another. There is no validated beyond-use dating for preparations made outside a controlled compounding environment; anyone offering a confident number for that is extrapolating.