It will switch off automatically at 50 mins, and I think you can run it three times before you need to run the engine (to protect the main battery), going off memory for the three times bit. I've only ever run it a couple of times and have switched the warm air heater if needed. My thermal wrap for the roof makes a difference for overnight heat, stops the wind chilling the air in the early spring/late autumn. Seems a long time ago that I have used heating for camping though, July 2020 was the last time out, and it was warm.