I agree with the "at their own pace" theory. I've got an 06 male pastel at just under 300g, an 06 normal female at just under 500g now, and have seen 06 normal females as high as 1000g.

This brings up another interesting point... I think BP owners measure more often in weight than length. Weight is generally a better indicator of health than length, as long as they're not obese.