We bought a custom made Adco cover back in 2006 for our 36' Diplomat. I put the cover on for the first year, but it was a nightmare. Mine was made from duck cloth like they use on boats. It was too heavy to carry up on the roof, so I had to drag it up from one end.
Eventually, I built a set of stilts behind the RV that supported a plastic garden box. The top of the box was at the same level as the RV roof. I could open the box and pull it right onto the roof. Even with making it easier to do, it was still a lot of work and I quit using it. It's still like new and stored in the same plastic box.
For us, we were using the RV once a month or more all year, so putting on and taking off the cover was too much. If I lived where I had to store it for the winter, I would cover it.