That's quite a few eggs, must have been expensive. What kind of incubator are you using?
I myself only stopped turning my eggs when I heard the first baby whistling, but I think it's safe to stop anywhere after day 50 or so.
It sucks that you can't candle these eggs; I candle everything else daily.
Instead of candling, you can set your eggs on a flat surface outside the incubator. It is a good sign if they appear to "lean" to one side rather than sitting level on the surface. You can also whistle and talk to them and, if they're awake and feel like it, they might wiggle in response. This is said to start around day 30, but I don't think I've ever seen anything before day 40 or so myself. That's a good sign too, but it does not mean that they're not alive if they don't; some eggs do a lot of nothing for 60 days and then hatch right out.
You can also go by temperature. If you feel the eggs after some time out of the incubator [like 5-10 minutes, I measure mine at both times before returning to incubator] a good egg will feel very warm in most spots with a cool spot where the air cell is. It's really difficult to tell by feel if they're alive, though. What's better is if you can find a thermometer kind of like the ones for industrial use or for taking the temperature of infants where you just point them at or hold them against a surface and press a button to test. Living eggs will remain very warm [above 90] for longer than non-living eggs due to the heat produced by the chick's body. Somebody on another thread described a more exacting method, and I am testing by testing each of my eggs in for spots [top, bottom, and both ends] at five and ten minutes out each day. I have one bad egg being kept for use in comparison, and I don't believe the test will harm the living eggs as the male sometimes stands up partially while nesting [In some cases they abandon the eggs later on in incubation for even a day or so, and they'll still hatch if transferred to artificial incubation], they're big eggs that won't lose much in core temperature, and my incubator lacks a fan so I think the fresh air will be helpful to them -hoping to transfer them into one with a fan as soon as I can get one.
Anyway I have noticed with my eggs [day 26] that they are about equal temperature all over when taken from the incubator, and then as time goes on they lose temperature -up to about ten degrees at most on the coolest part of the egg. The top of the egg remains warmest and does not get below 90. Bottom gets down around 90 as does small end, while the air cell end gets closer to about 82 before they are returned to the incubator. Since my known dud egg loses more temperature, does get below 90, and does so in a more uniform way I am hopeful that both of my "good" eggs are currently alive. I will only know for sure if I get some wiggling or hatching.
All of these are good for trying to get an idea of who is probably alive, but never throw away an egg that doesn't seem alive until you know for sure by stink, leaking fluids, or last time I hatched I had one that would swish when I moved it. I could feel it when I picked the egg up or turned it, so I knew that one was infertile; I still kept it until my current emu had hatched, but I knew for quite a while before that that it was a dud -I even named the egg "Dudley."
