I don't cover mine but I don't know of anything wrong with covering it. It would save having to inspect it in the spring for bird/wasp/bee nests. You might check Camping world for a cover.
I picked up A/C cover at local RV place. I wanted it for fall camping. Figured there was a lot of heat loss through the A/C. Used it this year and it seemed to help.
__________________
2008 Cruiser CF26RK
135 Watt Solar Panel
2013 Ford Eco-Boost
Heavy duty payload - Max tow
I cover both of mine, my thought is that it will sit for the next 6 months and it does keep the UV rays off the plastic schroud, and it does keep the snow off the units, I have always covered mine in the winter and never had aything get into the units, I got them at camping world, fairly cheap, just make sure you order the right one..