It can definitely change with time. Twice I have marked a few of my Jersey Giants as culls too early. Mainly because they looked too small and thin at the time and I was inexperienced. Waited for them to grow to go in the freezer. I went out one day and they were completely different. Better looking. It's important to let your chicks, at least in the first generation, grow as long as possible. That way you can familiarize yourself with how the line you have will grow over time. Eventually you can train your eye to pick out traits that, once you see it in a young bird, you know it isn't likely to improve.
