I guess just because they are still growing rapidly, heading toward sexual maturity. (I breed very few pairs each season; my goal is not to rush them to breeding size, but to get to a nice adult size in a reasonable amount of time). I feed every seven days from 200-300 grams, every ten days from 300-400 grams, and every 14 days up to 600 grams. Some of my 550 and up snakes are on a three week schedule and gain about 5-10 grams per feeding. Breeding females get fed on a shorter interval. Some females get a little pudgy near the vent at a young age. For the two or ree that have done that, I've moved them up to the next group sooner.