The place where we lose most of our money is in the mornings getting set up. Heating the sand, heating the bricks. If you can maintain the heat overnight you can stock the staging and just show up and mix up in the morning (use the box heaters in the "fire barrel" with a couple tarps on it). You have 0 downtime and almost all of your on site hours are productive. The cost of kero overnight doesnt matter, you make it back in the first 30 minutes when you show up.