Do you have a separate hatcher you can move them to when it is time for lockdown? (Day 18) If not, you could probably add them today but not after...
Once they get to day 18 when you stop turning, you need to stop opening the incubator until they are all hatched. So, if you had some in a week later, they would still need to be turned and you wouldn't be able to do that.
If you have a separate hatcher, (an incubator without a turner), you can put the eggs in there when you stop turning....so you could still continue to add eggs to your incubator.
I"m new to hatching too and actually just set my first batch of eggs yesterday.
My friend adds eggs to her incubator only once a week...but she has a Sportsman that has the hatcher on the bottom of it. Before that, she had 2 incubators going, one for hatching and one for incubating.
My plan is to get another bator, and use it as a hatcher...so I can have constant eggs going....but first I have to make sure I get the first batch right. That is what everyone has been telling me.
Ok So I have an automatic egg turner, Do I need to turn it off at day 18? T
Yes, and if you aren't trying to do a staggered hatch, you can remove the turner at day 18. Some people set their eggs (small end down) into an egg carton for the hatch, others of us lay the eggs down on the screen at the bottom. Don't forget you want to raise the humidity for day 18 - hatch.
I did my very first hatch which ended last month. It ended up have 5 waves of eggs in it and it was super stressful. I ended up having to build the MissPrissy incubator (off of this site) to use as a hatcher since there was a humidtiy conflict! It was fun but the craziness lasted for a long time, my records sheet was like chicken scratch in the end and I didn't have a chance to bond with the chicks like I wanted to since there were just so many! I ended up selling all but 3 (out of over 25). If you only have one incubator I'd only have a 1 day difference. More than that could cause probs.