According to Derek, this is a product of power feeding and leads to a very early demise. Unfortunately due to the price tag these snakes demanded years ago many people spent a fortune on them then proceeded to power feed them (easy to do considering their feeding response is insane). Unfortunately their desire to eat comes from their natural low fat reptile diet in the wild. Power feeding them jumbo rats makes them grow fast and become sterile adults that reach lengths of 10 feet only to die of fatty liver disease.
A healthy bhp that has been responsibly fed and grown should not typically exceed 7'. Depending on local you will occasionally get one larger but it is also not uncommon for them to top out at 5-6 feet (typical size of a woma).