Pitot heat: Battery 'on' until battery 'off'.
Bear in mind that it's cold & nearly always wet here so we tend to leave the thing on all the time. Time from engines start to airborne is frequently less than a minute or two so better it's kept warm.
Windscreen & prop anti-ice: Temp below ~2 deg C & visible moisture, OR visible ice
Wing de-ice: After ice accretes to ~1/2"