Great answer Joanna!!
I have a female BP that is around 4.5ft long, but only 900g. She keeps getting longer and longer without putting on much weight. Someone who didnt know might think that she is ready to breed due to how long she is. The most important part for a female (this is where the 1500g mark is important) is body fat; without enough body fat the female is unable to live for months without eating as well as produce a clutch of viable, healthy eggs.

I am going to be using the year round method going forward; IMO captivity lets us breed BPs whenever we can stimulate them to. This is benificial because we can breed according to the snake's weight and conditioning, rather than rushing an undersized/developed animal that only needs a few more months to be ready.
I've also been toying with the idea of a breeding room, with 'winter' photoperiod and cooler temps that I would move the breeders into. The one thing I havent really worked out yet is the best way to acclimatize them to the change. Not risking RIs or anything... sooo not worth it.