At work, where we dust constantly, we often notice an area, or a class of surfaces, that we have been ignoring or not seeing for a long time. Once you really look at it, you have to clean it, because it's filthy.
Today at home I picked up some windex and paper towel to clean the bathroom mirror. I turned around and saw the light switch.
I have now cleaned the upper horizontal and vertical surfaces of all the wall switches, switch plates, and socket plates in the bathroom, hall, and kitchen.
I'ts just a small cleaning project, but it was very satisfying.