I covered my last TT for one year. Actually only 3 months due to the cover ripping from the wind finally taking it's toll. Adco replaced the cover after 1 month of warranty investigation. I never used the new one but sold it with the camper.
IMHO it's not worth the hassel and will potentially do more damage than good. Now I wax my unit before the long winter and leave it outside. The covers can scratch your sides and wear down parts of your rubber roof where it rubs. I've seen some people use marine shrink wraps on their roofs which would be a good alternative, but I am not putting a flame to my unit.
So I am now of the 50% that say no to fabric covering based on my experience. If you are in an area with no wind or protected like a barn and want to keep dust and dirt off then okay.
Maybe a storage unit if rates are fair.
The cover will not help in anyway to keep it warmer. 40 below or 40 above it's still going to be cold until spring time.