I use two 700l/h external filters in my 270l tank (in reality with filter materials fitted they run about 300-350 l/h each).
As the filters are tall and the water starts at the bottom I have ceramic tubes on the lower level, bio balls at the next, course foam, fine foam and finally floss to polish the water. When the filter is cleaned the ceramic tubes and bio balls are just dipped once in a bucket of tank water. The sponges are dipped and agitated unless a bit clogged up. The floss is always discarded and changed. The bottom of the filter usually has a layer of gunk which is rinsed away.
I have always worked this way, going progressively from course to medium to fine floss and find the filter never clogs.
I would never have a form of media (apart from the top layer of floss) that ever needed replacing.
Filter cleaning is, IMO, only to remove excess detritus which may have slowed down filter flow rates.
I personally do rate ceramic tunes for their vast internal surface area and there ability to never get blocked up , unless you really leave your maintenance at too long an interval.
I have a pretty good handle on my filter flow, you can judge when the flow is reducing. Difficult to say how often to clean a filter, it depends on tank size, stocking, planting gravel cleaning etc. it's a gut feeling.
Sorry - got carried away with my answer. I'll shut up now !
