I fly in Northern Canada and our SOPs are to turn the windshield heat during our lineup checks. However, due to the weird visuals you get through the heated windshield, most of our pilots, including myself, prefer to leave them off until the after takeoff checks. We also turn them off for landing. In the summer, if we are in VFR conditions, we leave the windshield off for the entire flight...depending on the temperatures up at altitude of course.