How to handle lockdown with a staggered hatch

Hello, newbie here. I went a bit overboard ordering my first bunch of eggs and they came it at different times. I have 2 incubators, 1 for incubating and 1 for hatching. I will switch about 12 eggs to the lockdown bator on day 18. But 2 days later I will have 6 more than go into lockdown and again, 2 days later, another 6 will be ready. Can I open the lockdown incubator just long enough to place in 6 eggs? The last batch can stay in the first incubator but I just don't know what to do with the middle bunch. Any suggestions? My humidity has been staying between 40-43% with next to no water in there. Temp is right at 99-100. My "oldest" eggs are only on day 7 so I have time to figure it all out.