No matter what age they are i feed all my bps every 7-10 days. My 3 big girls, 1300 grams+, get rats that are roughly the same girth as the fattest part of them. When i buy a big bag of like 25 rodents i usually weigh one or two just to make sure that its within the 10-15% range (i only do that for my cinny male who is about 400 grams). For my three big girls i dont bother weighing their food, they just get a rat thats roughly the same girth as the fattest part of their body, like i said before.