I get tested at the Vets Hospital because of my meds and have had my frozen samples test good after 18 months. I keep them frozen until I get to the hospital, then go to the snack bar to get a cup of coffee and dunk my sample in it until heated. I have to shake it really good cause it will have floaties, but after it heats up real good the floaties dissolve. They dont check temp so I dont have to worry there but if they do just slap a hand warmer to your sample.