[JandC]

We keep both tanks open, I totally agree with Overlord about having to go outside and turn the other tank on when you run out doesn't really make sense (I have my own bunny slippers though).

When we are using the furnace, like now, I check the weight of my tanks every few days. It is obvious to me by the weight which one is close to being empty. I don't always wait for it to be completely empty before I take it in for refill. I have already taken one in this season that only took 20 pounds.