I have a question;
Considering the time and effort to put on and remove a cover, how often do you do this?  Reason being, I take my camper out about once every other week.  More in summer than winter, but I use it year round pretty much.  I'd be looking at 20+ times climbing up there to put it on and another 20+ times to take it off.  It would sort of defeat the purpose of making a getaway when the mood strikes or an invite to take off pops up I would think.  
I bought a cover.  Used it 2 or 3 times when I thought it was going to be especially bad weather.  That was enough for me to consider the risk of getting up and down so much.