If you aren't using the trailer, I would plan to put some RV antifreeze in your holding tanks, down all your drains. The holding tanks are exposed underneath. I would also plan to drain the water supply lines, using the two low point drains near the floor somewhere, depends on the floorplan. Those two things combined with running the heat if it's expected to drop near freezing should be ok.
However, don't run the heat if you cover the trailer. The cover could catch fire or trap carbon monoxide. It's pretty easy to winterize the trailer's water lines either using air or RV antifreeze, and in my opinion a lot easier than worrying about running the heat if it gets cold. You can buy RV antifreeze at an RV dealer, boat dealer, and even most hardware stores and Wal-mart will carry it this time of year.
Here's a step by step tutorial of how to winterize fully: http://www.sunlineclub.com/forums/f7...thod-8646.html
2007 T-286SR Cherry/Granola, #6236, original owner, current mileage: 9467.8 (as of 5/26/19)
1997 T-2653 Blue Denim, #5471
1979 12 1/2' MC, Beige & Avocado, #4639
Past Sunlines: '97 T-2653 #5089, '94 T-2251, '86 T-1550, '94 T-2363, '98 T-270SR