heater at nights?

I recently went to my local hydro shop(closest one to me,about miles away) to buy sum worm castings.
I was talking to the shop worker about my setup. I told him recently have have realy cold temps at night in the 30's, and that makes my room about 45. I have benn running a propane heater to bring it up to the 60s. I told the guy this and he told me i dnt want to run at night. He really didnt explain, just said that the plants release moisture at night. I dnt see why running my heater at night would be bad, could it be?

Run the light at night
You probably wouldn't need the heater if everything is insulated and set up well.

From what I understand you dont want your plants to get too cold, or you dont want there to be too much of a temperature difference between day and night. The big temp swings can encourage powdery mildew but otherwise are not bad. Cold nights will also cause purple plants.

As long as you have a 10-15 degree temperature variation during day/night in your room, you should be good. For optimal growth keep your lows atleast 60F. It's in the 20s here outdoors but my tent never gets below ~70F lol.

Thermoperiod refers to daily temperature change. Plants produce maximum growth when exposed to a day temperature that is about 10 to 15°F higher than the night temperature. This allows the plant to photosynthesize (build up) and respire (break down) during an optimum daytime temperature, and to curtail the rate of respiration during a cooler night. High temperatures cause increased respiration, sometimes above the rate of photosynthesis. This means that the products of photosynthesis are being used more rapidly than they are being produced. For growth to occur, photosynthesis must be greater than respiration.

You don't want increased respiration at night..

thank you all