I have a Top Hatch incubator that is notoriously bad for keeping stable temperatures. I keep it adjusted so that it doesn't get over 100 degrees so I tolerate an occasional dip down to 95. This last batch of eggs has been in there 21 days as of this evening doing the temperature swing thing. I lift the insulating towels this morning to check and see how things are going and lo and behold there is a chick. Early of all things. In an incubator that has been running cooler than optimal!