We live in a high altitude location (8,600 feet elevation in Colorado), and unless you cover your unit, the sun will TOAST your unit in a couple of years....And we have the pine tree sap stuff also....
I've used a cover on the last 3 motorhomes I have owned and they looked new as the day I bought them when I sold them....had no scratches or rubbing on the paint or decals...also, its nice to uncover and drive it away clean...
I only use
ADCO with Tyvek covers...dont use the "Classic" brand covers as they dont hold up well....
Edit after reading your last post: Don't even THINK about using canvas material on your coach....Im sure you WILL have cover rubbing problems.
You might do a search on
THIS FORUM on RV covers as they aren't just Winnie owners. This subject has been talked about for eons.