Get a few females bison. Breed out a baby bison and milk the females every hour. Cryo baby bison after every milking so you have an endless supply. Have a grown ice wyvern and store bison milk there, it stays for 3-4days in the inventory. Use low timer milk for baby wyverns. They don't eat a whole lot so you can put 3 milks in it and they're good for hours. I left mine out for days and only kept 2-3 milks at a time in its inventory, on official. Pve, 5041.