I tend to keep my cars forever. In addition to my daily driver, I've got two that are almost 20yrs old (bought new), and they do park outside all day, and the paint is sunburned, and if I don't do something soon, they will rust to dust.
I do not want that sunburn on my campervan! It cost way too much for that. Besides, the plastic parts (vents, ac cover, etc) on the top of my trailer has needed replacement a few times due to deterioration...and if I can avoid that with a cover between trips, I would like to give it a shot. I realize I will need a ladder...