You can't really go by age with ringneck snakes... Because different sub-species grow at different rates, plus there are factors such as gender and diet... as well as how often they eat.

With southern ringneck snakes, males are usually sexually mature at 9"-11" long, and females around 12"-13"...
But there is a population of them in FL (and probably other places as well) where the largest they can get is 9".

Can't answer your question about the unfertilized eggs though, any time I had a ringneck lay eggs I was waiting for them...
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Mike
KingPin Reptiles Inc.
www.kingpinreptiles.com