The trend I've noticed since I started researching ball python breeding is that the minimum age and weight that people find acceptable seem to be going down...

Ultimately I'm always going to look out for what's best for the animals, and I don't see myself breeding any females that are under 3 years, or under 1500 grams. I will probably even wait until 1800+ for most, as I've heard many breeders say that the longer you wait to breed a female the first time, the larger clutches she'll give you for the first several years of breeding.