I just finished my first hatch (last one was over 10 years ago so this all seems new again!), and I didn't have a high success rate. Put in 14 donated eggs (guy said, "I have a rooster so they might be fertile but I dunno....." and then 7 more from my own two hens. Short story shorter, four of...
I've never done this (gathering eggs and having to wait to put them all in the incubator) before. I have always just had somebody give me a dozen eggs, and then I hatched them in the classroom incubator (which I no longer have!).
I found somebody locally who will give me as many fertilized...