be-20 windshield
I have always believed the heat to be used for windshield life. At a higher temperature it is more malleable. Thefore, when the heat is on the windshield can deal with both temperature and pressurization changes easier. I have never had a windshield blow out unless at full pressurization. I also believe that the shield heats should not be on until after takeoff simply because of the distortion of view.