No. Last year was about 50/50 but I had a few smaller girls I didn't really expect to go. It does help the males have higher sperm counts when they are cooled though so if you can cool them, I would recommend it.
We had two together completely out of season for a few hours once and had eggs (we were originally told the male was a female, so woops on our part). So it's not completely necessary for sure. But if you're having trouble, it can help.