I have 2 hatch dates 8 days apart in my incubator. After day 18, I still have to open it to turn the later put in eggs a few times a day. It seems that everyone says this is an absolute no-no, but doesn't a hen have to get up and do her business the last three days also before "she" explodes?! I don't see the harm in opening the bator for the short time it takes to do this and will do so. Think of the eggshell as a styrofoam cup, and the egg contents as a cup of hot coffee inside....., in the short time it takes for the temp/humidity to restore itself, did your coffee get any colder? I don't think it matters much, the internal temp holds much longer than the air temp surrounding the eggs! Just my thought and I have to do it! We'll see on the 9th and 17th how my hatch goes!!!