I say, “Keep them clean.” Regular cleaning of windows, screens, and solar panels reduces the corrosive effects of dirt, moisture, and contaminants … All that to say, “The regular cleaning of these surfaces will protect your investment.”  The window cleaning and screen cleaning will also reduce the number of insects, spiders, and bugs that will congregate around window frames and at times make their way into your home.
Did you ever notice how the windows with screens seem to get dirty more quickly? Stuff builds up on the screens and then migrates to the glass. The dustier the area you are in (like a high traffic volume area where road dust is kicked up) the more you will notice quick buildup of dust on your windows. If you have a number of trees that overhang or are near your home, the more needful it will be to clean the windows and screens on a frequent basis.  Dust & pollen from nearby trees will accumulate on your screens.  Lastly, if there has been construction nearby, the construction mess on your windows/screens can be significant!
So, what to do?
Frequently wiping with a damp towel or light brushing of the screens in between cleanings will cut down on the dirt transfer from screens to windows. That transfer occurs when the wind blows overnight moisture that collects on the screens onto the windows. Wind and rain combined also move the dirt from screens to glass. If the screens are clean it will cut down on the dust that moves from the screen to inside you home when those windows are open. However, the best way to have sparkling windows and clean screens is to bring in Blue Ocean Window Cleaning on a regular basis. With regular cleaning you will be protecting your investment.