You are right, IMHO using the aircon all the time not only builds up a reserve of moisture in the system, it also encourages bacteria and fungus / mould to breed (which thrive in the humidity) - these cause bad smell, but even more worrying can cause asthma attacks and general bad health (the 'sick office syndrome' which makes office worker ill was blamed on pathogens breeding in the airconditioning pipework and filters combined with sealed windows which allowed no fresh air in).
I normally use the 'clear screen' feature in certain cases (even to cool the car down in summer), but other wise will only run the aircon once a week to keep it in decent shape. I do not like the way that when you select 'auto' the system forgets all your manual settings and you have to tweak them back in when you revert to manual, also system will not keep a stable temperature when not in auto with aircon on, even when outside temperature is well below the temperature you select and you would think aircon would not be required as all you need is heat