iMac sans glass?
Abbott Schindler wrote:
I also hadn't heard the part about needing to clean behind the glass at any interval, let alone annually.
It depends somewhat on the specific iMac model as precise paths of the airflows differ from model to model. And it depends naturally on how clean the air in your room is.
But dust and dirt is an issue with every technical device that has (unfiltered) airstream flowing through it. It is good practice to clean all kind of devices internally occasionally, eg, the fan bearings in any devices with fans or all surfaces that have an optical purpose like monitors, camera sensors, lenses.