Use aged egg whites for better meringue stability by resting them covered in the fridge for 24-48 hours. Sift dry ingredients at least twice for a smooth batter. Do not rush the resting period to prevent cracking. Use an oven thermometer for precise temperature. Store filled macarons refrigerated for up to 3 days; unfilled shells at room temperature for 5 days or frozen for up to one month. Let filled macarons mature in fridge for 24 hours before serving for best texture and flavor.