Per, I'd be as much concerned about the drains and faucets themselves as well as all of the OTHER plumbing fittings that AREN'T PEX. As long as you have the water heater and furnace
running the inside stuff isn't likely to freeze. If you're going down the road the next day for more than an hour or so with water in the lines, drains, tanks, and faucets there's a potential for problems.
I use mine late into November and December after I winterize, and begin again in late February or early March (depending on snow... I don't tow in snow... cold doesn't stop me) but I typically use a porta-potty in the trailer, and "dry camp" with bottled water and a tea kettle for a water heater. I use a plastic wash basin in the sink rather than the drains.
One of the biggest issues for me isn't winterizing/dewinterizing/rewinterizing, but finding a nearby place to dump the tanks that isn't frozen. And then, of course, there's no fresh water to rinse the stinky slinky or any of the fittings. The wash basin contents just go discreetly out the door to an appropriate place, and the porta-potty can be emptied in any toilet.