Consider running the heater on high temp for 5 mins before shut down. Short cycling at low temps can result in gumming of the screen.
Also, if starting the heater from very cold interior temps, the heater will likely cycle twice. The combustion chamber needs to get warmed up. I have on occasion, when starting from very cold temps, held my hand across the outlet vent to help the unit warm up a bit quicker. Kind of like an Exhaust Back Pressure Valve