A supply hose in outside conditions could freeze in under an hour. The inside areas of a coach take much longer. The pipes inside, depending on what type you have, can freeze, expand, and return to normal after freezing - IF YOU'RE LUCKY. Replacing frozen pipes and fittings wherever the freeze MAY require removel of wall panels etc. - there's no reason to allow this. Never leave the water on to the coach - don't rely on ANY system to keep the coach heated. If it isn't winterized, check to be sure it is heated. Pour antifreeze into drains and traps - a frozen trap can leave a slow leak which will cause a lot of damage over time. I once had to remove almost the entire bathroom to access the tub drain system - no fun!
I would always heat my coach while it waited to go to warmer areas. I felt it was worth the utllity coast vs. the cost to winterize. I kept a freeze alarm light in the window for ocasional checks.
