If you do not know the history on the snake, or if the snake is underweight or has any other problems, then sometimes a reluctance or inability to poop can signal parasites. I learned this first hand with one of mine. In that instance, I knew that his history was a bad one, and on top of that he was also severely underweight. He would eat and eat and eat and never poop. We went a month and a half without a poop before I finally took him to the vet. Turns out he had three types of parasites (which I'd already suspected).

That's not to scare you or anything, and of course that scenario is not necessarily the norm. It is just something to keep an open mind to, particularly, as I said, if you do not know the history of the snake.

As for my healthy snakes, Adalae will poop sometimes twice a week. She's a glutton. She eats her food, expels the waste, and is ready for more within just a few days. She grows like a weed; it's wonderful. Some of the others who are just as healthy will only poop once every two weeks. It varies from snake to snake.