Its all about how well they eat....I don't really think in terms of length, but I'd say the 600-800 gram range is about right for a yearling with optimal husbandry. I picked up a 2 y/o female that was about 780 grams small about 4 months ago, and has already passed the 1000 gram mark and keeps eating like crazy. In other words, it depends a lot on how they kept, how much they eat, etc.