I find my winter camping gear is good down to roughly about ten degrees. Colder then that things get potentially dicey.

• My stacks of sleeping bags are comfortable down to around ten degrees, any colder and my feet and hands start to feel cold at night.
• It seems like my truck’s starting battery and load from thick oil increases at below ten degrees, leading to somewhat sluggish starting after a night of opening and closing doors.
• My propane heater throws off less heat below ten degrees, the camp stove cooks slower and the lantern is dimmer due to propane and condensate starting to conjeal in the lines and regulators.
• House / Accessory Battery voltages drop leading to them tripping out due to under voltage much more quickly.
• Much greater risk of the propane heater or stove malfunctioning due to conjealed lines from condensate and jelled propane, plugging up regulators and propane lines.

I’ve camped a few degrees below ten degrees but it’s not pleasant and leads to more headaches then it’s often worth. But above ten degrees generally things are smooth sailing with the gear and set up I have.