Someone please correct me if I am wrong!
Media with internal pores (ie bio-chem stars) work well for a while but eventually the pores become blocked and the bacteria residing in them die. This makes only the surface of the media useful for bacteria. Also, the dead bacteria in the pores add to the bio-load and are essentially another waste product. This is why it is recommended to replace it every "x" months.
If you begin with solid media (ceramic noodles...)you won't have fluctuations in your bacteria colony from switching some of the media every "x" months.
So (assuming I'm correct), it's 6 for one and 6 every "x" months for the other.
Bill