Young snakes poop less as they use more of the prey for growing! If they are pooping alot then they are probaly being fed too much! 4-6 weeks is pretty normal. They will poop after every shed usually! They can go up to 2 months without a poop! If they are backed up then you can see it because the are large and hard near their vent. In this case, usually a good soak in warm water will get them going!