You never need to change the Biomax. They just tell you to do it so you will buy more products.
I don't even rinse mine out that often. The ceramic rings don't really collect enough stuff to slow down the filter in any way. The sponge needs to be cleaned about every 2-4 weeks IMO
. Like JC said, be sure you rinse the parts in old tankwater during your water changes, never in tapwater.