I just got my guy tested again and was worried about the timing of mailing the ACTH/Insulin/Glucose to the lab since the vet was coming on Friday.  I talked with Cornell and as long as the vet spins it out as per the instructions within 4 hours, it can be frozen and then sent Monday morning.  I never knew this and since I'm in a barn where the barn manager schedules the vet in while she tries to accommodate my schedule that doesn't always happen. So knowing it will keep frozen for a few days before the expedited shipping helped me.