I am a field shooter which means I face very high humidity like 92-93% during the night and in last 3 years I had only once (1x) a problem with dew - and it was caused just because I removed (detached) the camera from FW and telescope and mounted some filter in the field and therefore let the humidity (water) creep in.
The CCD is too small to have dew problems, really in my extreme conditions it is perfect and no worry about! This is a great advantage of small chips.