45 minutes of idling time per day in January in northern Alberta. I have a bunk heater and diesel-powered motor heater. Keeping the idling hours down makes the DPF system work better and it reduces motor wear because the motor is not running below its engineered operating temperature.
At -40 I set the motor pre-heat timer at 1 hour. Nice quiet sleep (provided no one parks a noisy Cummins ISX 15 motor beside me).