I tried covering my 2H trailer for couple years. Got Beverly Bay cover that ripped already on 1st year, and basically was gone by the end of the 2nd year. My neighbor never covers hers and it looks great (it's 20+ years old, alum). I think if you keep cover on all the time the moisture indeed will be trapped under (which is no good).
"Life isn't about waiting for the storm to pass: it's about learning to dance in the rain..."
"When we are no longer able to change a situation - we are challenged to change ourselves."
"How people treat you is their karma; how you react is yours."