I know that many of us use vaseline or bag balm on our chickens combs to prevent frostbite when it gets "really cold" at night. We must all have some rule we've made up in our heads of what "really cold" is. I'm constantly amending this rule in my own head, but typically I grease them when the forecast is somewhere between 20-25 degrees and under, and I've never had to deal with frostbite. What's your rule? And do you grease them every night if you're going through a cold streak, or do you have the belief that the vaseline or bag balm will last more than one night?