We use to cover a couple of our previous travel trailers, but we eventally realized, if we use the camper in the winter, it's a horrible job trying to remove that cover when there is snow and ice on top of it.
Here's the new rule of thumb (in my opinion)... if you have no plans on using the camper during the snow months, then cover it. If you have plans to use it during the snow months, then don't cover it.
I think this is a bigger factor than securing it tightly down, wind blowing damage and all that. If you plan on using it and there is snow on the roof, you are in for a real job getting that cover removed, and you WON'T be covering again when you return home.
