I used to have a Juwel Rio 125
Ignore everything Juwel says.
Fine blue sponges - replace only when they go into holes or won't go back to shape after squeezing.
Coarse blue sponges - as for fine blue sponges.
Green nitrate removing sponge - doesn't actually do anything. Pretend it is a blue sponge and treat accordingly.
If you have cirax, replace when it starts to crumble.
Black carbon sponge isn't needed at all on a routine basis. Carbon gets full after a few weeks and stops working. If you really really want to run carbon full time, replace every month. Otherwise throw it away and keep a spare in the cupboard in case you ever do need it to remove medication after treating sick fish.
White pad - won't wash more than once without going into holes. Replace after one wash. But don't buy expensive Juwel pads - get a roll of filter wool (filter floss) and cut it to the same size. Much cheaper.
Manufacturers tell you to change the media to make them money. As you can see, sponges and cirax will last for years. They only need washing in old tank water. When they do start to go holey/crumble, only replace one sponge or cirax at a time, with at least a month before the next one.
The only thing that will need changing regularly is the thin white pad that sits on the top. It is first in the direction of water flow; its sole purpose is to catch bits to stop them reaching the sponges, and it clogs quickly. It is not a very good home for bacteria so if you change it every other water change firstly it never grows many bacteria and secondly it won't have time to grow many - so you won't throw many bacteria away when you change it.
PS I have found a use for old unused blue sponges. The air pump that powers the filter in the betta's tank sits on top of one to cut down vibration noise