Carbon is mostly saturated within 3 days, regardless of type, according to the testing that I have found on the net. This claim has been supported by the effect I have seen on soft coral polyp extension when using it on my tank, as well.
Filter material that incorporates synthetic polyesters and / or resins, such as Chemipure, Polyfilter, or Purigen last longer, but your mileage will vary. It all depends on the bioload on your tank and the contaminant profile that the particular filter media targets.
The bad thing about Chemipure, in my opinion, is because of the presence of carbon, etc., you cannot see the color change when it is saturated, unlike the other two products mentioned above.
The color change of a Polyfilter, for example, tells you alot about the effectiveness of your other filtration systems. If it turns brown in a week or so, then your skimmer is probably not good enough, as brown indicates an excess of organics. If it turns green, then it is absorbing copper, etc.
I used to be a big fan of Chemipure when I ran freshwater tanks many many years ago. Unfortunately, despite their marketing hype, the claim that Chemipure is effective for 6 months does not stand up in the light of any serious examination or testing that I have seen to date.
Kent