I'd like to share something that I discovered. When candling my shipped egg last night it dawned on me that the air cell is perfect! I have never seen, in all the shipped eggs I have hatched this summer, an air cell this good. They are always large and irregular from the  air cell being ruptured from rough handling by the post office. After reading on some other sites some tips on getting better hatches out of shipped eggs, this time I let my eggs sit for 2 whole days before starting them, then after I put them in the incubator, I waited a whole other day before turning on the turner. Looks like the extra time allowed the air cell to go back to normal clap I just won an 
Ebay auction for 8+ bantam Polish eggs that are coming from Kansas to me in California next week and I am going to try this again with them and see if I get the same result.
This is very interesting, I am curious to find out what you discover and Thanks for sharing that!   I let my shipped eggs set for about 30 hours before setting but I did turn the turner on when I put them in.  I don't have much experience looking at air cell's yet so I couldn't tell you if mine are good or not, I am guessing they are average for shipped eggs. 
I am trying my first hatch with shipped eggs and I am really confused by what I saw when I candled today, some fairly clear eggs with veining and movement and other eggs that you can't see through!  All are light brown or cream colored on the outside and some are porous as well. 
I go to lockdown Wednesday night at midnight and I have all Sussex (light, coronation, buff, silver and 2 possible reds) and 1 Serama sent for a friend...most of the light colored birds don't look as dark but then one of the light's looks dark and another doesn't...but that could be a mismarked egg as I got a light chick out of a shell that was marked Buff on a previous batch my friend hatched for me and there was only 1 chick out of 12 eggs)
I have pulled 4 bad eggs so far and started with 21 eggs (these were replacement eggs for the 2 previous batches with 1 chick hatches), three looked 1/2 hard boiled and one had black goo inside and smelled like sulphur once I opened it , but I pulled these because they had just started to leak and had what I call shadow cracks in them when they arrived so I was watching them closely, nothing else has leaked or smelled so I left them all in there.
Is there that much discrepancy between chicks that some eggs would look black and others would look only half grown?  The Sussex are a pretty large breed (these are from the Australian imported lines originating back to greenfire farms and I am wondering if they just develop slower and if they do should I put off lockdown for a day or so?  The breeder won't respond to my emails anymore, perhaps I asked too many questions or they are too busy (I can relate) but I am not sure what to think of this and any input would be appreciated!  
With no other feedback my guess would be to go into lockdown on day 18 as planned and if they seem to be taking longer to hatch than normal (some of them anyway, then I will be prepared to open the bator and get dried chicks out after 48 hours (the most they can go after hatching I read) and leave the rest longer to see what happens...I have them in a bathroom with the light off and the door open (for fresh air to circulate in) and it has no windows in it but I could crank up the hot water and get it nice and steamy in there and bring the humidity up before opening the bator to try and keep the humidity from dropping very much..not sure what else to try but it would be worth a shot if they seem to continue to develop as they have been even though some appear to be slower than others.  
The Silver Sussex chick I have that is about 3 weeks old that a friend hatched for me from the first batch (lone chick from 10 eggs) is taking a long time to feather out but her body is getting much larger than the speckled I got from the feed store to keep her company and the speckled has lots of feathers, the Silver is few days older than the speckled and I have read that the Large Sussex take longer to mature for table birds also so that might make sense...
Anyway, almost time for lockdown (I think anyway) and it is getting exciting now ! ! ! ! !
I am with FarmGirl, it is going to be a VERY LONG 36 hours!!!!