Common wisdon states indefinately but I am certain there is a point that there would be changes due to dessication unless the embryo is stored at absolute zero. At the present time the FDA/AATB limits tissue for implantation into humans to a shelve life of 5 years unless viability of a longer shelf life can be validated. I do know of several cases where prior to this regulation we implanted Cryopreserved Heart valves that were almost 7 years and they functioned normaly.
I do not know of any regulations on Bovine reproductive tissue. Does anyone know if this is regulated ????