Umm...were these eggs sold as fertile HATCHING eggs? If not, at some point they were possibly washed, sanitized, and refrigerated. Unless they were on a shelf that rotated at least 4 times a day so the embryos didn't stick they probably won't be developing. Have you've candled them for fertility? I hope you don't have an 18 day mess under that hen.
Some people believe that fertile eggs have a higher rate of digestibility or are lower in cholesterol, maybe they are more nutritious, etc. Unfortunately, this is perpetuated by doctors as well. You know the only difference? There are up to 20 chicken sperm in there, potentially. Nothing that is going to effect the nutrition OR the taste, not going to make any difference, especially if they are chilled. There is low to no potential for life once you go through the cleaning process. But hey, miracles happen everyday. Until someone hatches out of those eggs, I wouldn't call. They are probably some type of RIR sexlink/hybrid, nothing rare or exotic to be sure.
And her getting off the nest would have no bearing on the hatchability. They do a much better job than we do with their eggs and they come and go as they need and as the eggs need them to to regulate temp. I've had a few 100% hatches in my time, but my ducks have had 4 100% hatches in 2 years. They seem to get it completely right every time.
