You should generally change the carbon filter every 3-4 weeks. You normally only have to use carbon filters if there is a smell in the tank, or you want to remove discoloration.
It is important to change the filters on your pitchers regularly. On average your filters should be changed about every 40 gallons or roughly 2 months.
Check it at each oil change, and replace when dirty.
There is no specific set time that you should change your filter. I would check mine on a weekly basis and if it was dirty I would replace it.
Carbon filters function because of SURFACE presented to the filtered liquid/air. The greater the size of a filter, the greater the surface presented. The carbon in Carbon filters are often ground to a fine grain for the same reason, as the smaller the grain, the more surfaces per unit weight.
If this is a technical question then: Carbon filters or more likely activated-carbon filters have the effect of absorbing certain airborne chemicals, often those associated with bad smells. Most carbon filters are ineffective due to size limitations. i.e. in vacuum cleaners where the filter size is too small to absorb many of the bad smells. Activated carbon granules are also added to liquids to do much the same job of mopping up unwanted chemicals, they are used in brewing and distillation.
Not often if there tarting to wear and tear you should replace them.
"This depends a lot on the filter and also on how often the hot tub is used. Again, while filters vary, most recommendations are to change the filter once every 6 months, more often if the tub is used heavily."
The owner's manual recommends that they be cleaned monthly and replaced when necessary.
The Holmes HAPF60 carbon filters will last for 3 months in the average household, extending the life of your regular air filter by trapping over 4000 chemicals as well as allergens such as cigarette smoke.
In dusty conditions, or with extensive idling replace fuel filters every 15,000 miles.
How often should you change water pump in a boat
Replace headlight bulb only when blown.