But like the others have said, they all grow at their own rates... I have three boys all born in July '09, and they weigh around 500, 600 & 800g respectively. Yes, the last one (Julius the mojo) is a porker!
Another good example of how they grow differently. My Pewter who hatched in August '09 is only about 300 grams empty and has an awesome feeding response.
My previous '08 Pastel is 360 grams empty. He is a picky eater.