use of interior portable heater during storage

I've done it for periods when I was going to be using the TT soon and the cold wasn't going to last for long. As said, it's pretty quick to just blow the lines out. The oil filled radiators are the safest portable. Open cabinet doors and try to set it for about 50. That should keep anything from freezing on the Oregon coast. In extreme cold I agree this probably wouldn't be ideal but that region is just not that cold.