i wait until after v day to tap anything.. maybe a bit longer depending on the forecast. depending on your operation it maybe be easier or harder to make the right choice.... i like to wait till it looks and feels right to me, even tho it was tee shirt weather in my area for a few days my test taps didn`t do any great so the wait continues.... my reasoning is that there is nothing worse than dealing with frozen releasers and keeping flu pan from freezing in prolonged cold to start with nevermind all the other headaches down the line to get to finished syrup. choose your window wisely , because impatinces can turn into a headache till the weather gets better atleast with sugaring that is . good luck