The very fine white filter (think is filter wool) should be replaced each time the filter is cleaned, as its not meant to be cleaned and put back. The blue sponges and media can however be cleaned and put back. Not sure exactly but think the ceramic media should be replaced yearly (anyone confirm?) with half the sponge replaced every 9 months.
Depending on the bioload within the tank, an external filter like yours should only need cleaning every few months (2-3).
I would add that, I have 100% sponge in both my eheim filters. The media stuff is expensive and a waste of money IMO, both mech and bio filtration can be achieved just as well using course and fine (and if you want, the filter wool as well, but I dont) sponges. So save yourself some money and when you come to replacing the media get sponges instead. I also dont replace mine every 9months, dont see the point, perhaps every few years, but no more often.
Sam
