I have a Brinsea Octagon Autoturn which I use in an unheated, north-facing outhouse room where the temperature and humidity stays fairly stable. I leave the air intake half-open all the way through incubation, reduce the temperature from 37.4 to 37 degrees on day 18 and add half a cup of warm water to one of the channels on day 19. I open the incubator only once a day, unless I've noticed an egg pip but then no progress made for a couple of hours. I take the rsik at that point that the chick has run out of energy or is too large to continue the struggle to hatch, slide the egg out, carefully break it open and replace the chick. The chick generally then survives and thrives - occasionally it won't. Sue Hammon, of the Wernlas Collection, told me they never add water, as our maritime climate means the air is generally humid enough as it is.