My PGD embryos are in Sydney and I have the choice each 6 months to renew and keep them frozen, to donate them, to let them succumb or donate them to science.
Where the frozen embryo donation also falls short is do you put a limit on how long you can keep your embryos for? Personally I am done, but there is nothing to stop me putting back and embryo even in another 20 years, so you would just say I still want more babies.... it would just be too hard to make that kind of ruling.