Well I agree that most powerfed snakes don't make it past 5 years or so but snakes never stop growing, its just during the first 3-4 years that they do most of their growing and that is why if you feed them very generously during that time, they will grow bigger if that makes sense. For example, you got a baby boa and you feed it every 10-14 days for 4 years. Then you got a baby that you feed every 7 days. That second baby will achieve a much bigger size than the conservatively fed one. That is partly how people can keep their boas on the smaller size and how people do it with retics too. Now yes genetics will play into it as well but that is end size. So like I said, the second boa will be probably 4'or so by the end of the first year and the first one will be 2.5-3'. And I also agree that most BCI are crosses somewhere and that goes back to the genetics end of the equation but again that is only part of it. Food is the other part. A good example is dwarf and SD retics. They are much smaller than their mainland cousins because of the food supply that was available. Mainlands got big because they had lots of food while the island guys didn't.

As for bone dry, that's why you run a humid hide. The boa can regulate the humidity it needs and no house is going to be bone dry anyways. I'd guess most peoples houses sit in the 30-40% range so uping it by 10-20% isn't really too hard. Maybe where you come from Eco Earth is cheaper but here in Washington State, aspen is pretty cheap. I buy it from Walmart for a smidge over $3 for 20 quarts. Aspen is much easier for me as I do complete cage cleanings monthly so its much easier to scoop up aspen, throw in bags and then vacuum the cages, spray em all down with Chlorhexidine, wipe em out and throw new aspen back in. I used Eco Earth for a year and I hated that stuff. It got all over everything, got dusty if it dried out and with using 2" of it, my big girl would pack it down from her weight which I'm assuming is the reason it molded on me. I had to throw out all the Eco Earth, all the wood she used to climb on as that molded where it touched the Eco Earth and tear down the Pro-line cage and completely scrub each piece and then put it all back together. That's when I switched to aspen and didn't look back. Now aspen will mold too if it gets wet but I use large heavy water bowls that even my big girl cant tip over.