[Peterbug]

1. If you have trees over the camper, you will have regular deposits of fine tree sap and possibly tannins from leaves in the fall. Sap holds dust, dust feeds green growing light utilizers commonly called algae. Regular cleaning will be required to keep it looking good. Covers can be the sacrificial protector of the painted surface, and are considered a 'wear item' to be replaced on a basis determined by the level of biological challenges being thrown onto your particular location.
2. Covers protect from UV ray damage and algae, but they sometimes hold IN the moisture when temp and humidity changes bring moist vapor into the interior, as well as small leaks. A dry cement parking location helps reduce the moisture coming up from the soil, but does not prevent all moisture. Finding a cover that breathes, and fitting your cover with breathing room can reduce the time that moisture stays on the surface between the cover and the camper. 2,000 years ago the Roman architect Vetruvius specified an air gap between a building's cladding and the interior air barrier, and modern engineer Joseph Lstiburek reminds us to always design the drying process well. Look for ways to have a 3/8" gap between your camper and the cover and you will have much better and regular drying. Dark colors on the cover will also aid in accumulating a little heat for winter drying. I have seen people use foam pipe insulation (pool noodles) under the cover, full thickness in the center and tapered as ribs to the edge of the camper, with an inch of overhang to hold cover off of the side. One super noodle down the center like a keel. The fancy 'breatheable' covers assist with this drying, but they do also tend to collect more dust as they are not shiny like a waterproof tarp.
3. "It's always SOMETHIN" - Covers with air gaps assist with moisture, but also provide shelter for critters. Wasps love to camp, as do mice. The defenses range from static barriers to active surveillance and remediation. Just as parents and babies benefit if the parent has a loving song to sing while changing diapers and doing laundry, campers need a camping song to sing while regular surveillance and maintenance is performed. Welcome to the world of people who own their campers instead of renting campers. Take solace in your self-sufficient camper lifestyle. And always plan for a wasp nest to be under the next hatch or flap.