I have that heater for my OR Teardrop.
I only need to run it on a shelf in the teardrop for 10 minutes at night and a few minutes in the morning in the high teens. It doesn't take much to heat up our tiny camper and body heat does the rest through the night, even with venting.
Great little compact unit, puts out less condensation than propane and burns more efficiently.
You just have to stuff the butane canister inside your jacket for a few minutes to warm it up on those colder trips before using it.