I say cover.. with individual panels. Esp with Lexan windows - yes, caution is required to avoid scratching, but without they will be opaque in 7-8 years.
Every honest marine canvas guy I know advises against covering and these guys are quite reputable. Their argument "for" is one of increased revenue for the canvas guy trying to sell you more work.
The windows below were Strataglass and 9 years old when the photo was taken on June 13th 2009. The dodger was installed in May of 2000. This canvas spent nearly 4+ years in the equator range then the remaining, in-between and 5 years in Maine.
Proper care, with the proper products, will help them survive longer than a cover. These were treated once a week or every other week with Strataglass specific products.
Polution fall out, grit and dirt stuck in the weave of the Sunbrella covers or in between the covers will permanently create micro scratches in the glass when the wind blows. This then leads to degraded visibility.
Again these Strataglass windows were 9 years old when the photo was taken and FAR from opaque. NO COVERS were ever used..
Believe it or not the Sunbrella wore out BEFORE the windows..
Please feel free to look at the full size image:
Dodger Windows 6-13-2009 (LINK)
This is our new dodger & windows they will absolutely not get covers..
For those who doubt my sentiments you are welcome to visit me at the Mobile Marine Canvas booth, where I work every year, at the Maine Boat Builders show. You can the speak with Seth who is arguably the best marine canvas guy on the Maine coast, and hear it right from the horses mouth. He will even give you case by case instances with actual experiences he can share..