Hold on, Midnight. Nobody said your animals were poorly cared for...they said it could be better.
Calci-Sand is horrible. IMO, the worst type of particulate substrate. Pick some of it up and look really closely at it. See all thoser tiny, jagged edges? See how it kind of looks like little puzzle pieces? That's how they act in the digestive system of a snake, too. They clump together, interlocking and causing impactions. You don't need a link to prove this, look at it, and get some wet in the palm of your hand. That's called "clumping". GREAT for cat litter...not so good for digestive tracts.
Now look at your ground English Walnut shells. See those sharp, pointed edges? They cause cuts and scrapes which can lead to infections. It's also quite uncomfortable. Don't believe me? Try sleeping with a few grains in your bed. Again...you don't need a link to prove it, just grab a handful, look at it closely, and than squeeze it tightly in your hand. OOOPS! Careful, did you cut yourself? Stuff is sharp, ain't it?
And just as a matter of fact...ONE snake for 15 years does not make a good base from which to make projections about your husbandry. 50 snakes for 15 years? You're getting there. 100 snakes for 25 years? That's better. How about the combined thousands of snakes over the combined hundreds of years that we have as a unit in this community. Gives you a little broader study group to work with, don't it?