We have had our chickens for a year and a half now and they are actually egg-cellent layers ;-) We have never had lack of eggs even when the girls were molting.
However, few months ago I started noticing extremely large eggs in the laying boxes. They are also a weird shape but never really double yolked, which I read they might be.
Well, supposedly there is nothing wrong with any of those overachieving hens and it can happen on occasion. I am only concerned about the pain they must be in when the egg is coming out - ouch! I should check their private parts for any damage or even a stuck egg. That happened to us once before and we had to remove it by hand being careful not to break it while still half way in the chicken. Anyone knows more about this subject?