There's really no general rule to how often chimneys should be cleaned, however a thorough chimney inspection
will help determine if chimney cleaning is to be done. This should be done once a year in general.
After a while creosote, the residue from burning wood, will start to form around the interior walls of the chimney, a build up of 1/8 of an inch or more requires cleaning.
It's important to keep your chimney clean
not only for efficiency, but to also preventing the built-up creosote from catching fire resulting in a flue fire. These fires can be very dangerous.
Although there are many do-it-yourself cleaning equipment to handle chimney cleaning
, it's also best to consult with professional chimney cleaners