I'd probably have the covers on all the time unless I was using them in fog or snow, maybe really bad rain.
Funny thing happened on the way to installing them just now...I mocked them up on the bumper and I'm getting cold feet about mounting them on such a clean, stock truck. It's 22 years old w 233k miles but dang is it still pretty.
I might put them on my RV instead but it has a pretty face as well. Thoughts?