[JRTJH]

A consideration (at least for me, when I parked my RV outside) is removing the cover in the spring. If you plan to use your RV early in the spring, before all the ice and snow have melted, getting the cover off the roof is nearly impossible. So, if you do decide to cover it and have any plans on a "mid winter escape" or an "early camping trip on that warm weekend in March", you'll have a tough time getting the cover "unfrozen" from the roof.

If, however, you don't plan on using your trailer until after all the ice and snow are gone, the flowers are up and blooming and the A/C is running in the house, then it wouldn't matter about the cover being frozen to the roof.