Directly in proportion to how much they eat- my baby girl eats like a horse and poops every day, at least once. My older dragons don't eat as much (5 supers every other day, daily salads) and poop closer to 2-3x a week.
beardies under 1 year typically poop at least once a day. older beardies poop less. ours is 4 years old and poops once a week. we were so worried when this started, but we found out this is normal...