Well, of course they don't all survive to live long lives. But that can be said of any species.
They're obviously built pretty efficiently if they've survived as long as they have while other species have died off.
I used to put cardboard down. But I found that more often than not the snakes dragged the prey off it anyway.
Thousands of feedings so far, not a single impaction, not a single time I had to intervene to remove substrate.