I have just done this and all is well
Sponges due out last Sunday and had forgotten to phone the vet before the weekend and organise PMSG.
Through best friends help managed to get the PMSG on the Monday and sponges came out that evening - 24 hrs beyond 14 days.
Put the ewes in with the tup at 36 hrs on the Wednesday morning before work. One tupped immediately! then when I got home from work all the rest marked too.
So .... didn't cause a problem but would be interesting to see what the vet says.