Buttered Side Down

I want to know why fate does this. I've been on the road now for over a year and half. Since we have two 30 gallon propane tanks in the RV. You switch from one tank to the other when one runs empty. Needless to say, it always runs empty on one tank in the middle of the night. It's like the toast you drop, does it always land buttered side down. I'll hear the heater click on and fail to light. It'a always 3 AM in the morning. Getting up out of bed at that time of the morning to go outside, to switch to the other tank wakes me up to the point I never get back to sleep immediately. I mean it never fails.