It could be that the ferret(s) in question needed a larger dose.  My Nova
was on Lupron for three years with great success, but despite her tiny
size, she needed a DOUBLE dose every THREE weeks.  Also, the Lupron is
pretty expensive; if you vet has few clients who need it, he might be
trying to store it for longer than it is stable.  My vet, Dr. David
Kupersmith in Cherry Hill, said that from he was uncomfortable storing
opened Lupron any longer than one month in a freezer (about -200C).  Any
warmer than that, and it probably shouldn't be stored at all.
 
Jen
[Posted in FML issue 3793]