Most stove inserts are installed with a metal flue liner. This liner protects the chimney from the high heat generated by the insert and makes cleaning easier for the chimney sweep. However, the sweep may need to remove the insert (if possible) or use specialized techniques to clean the entire flue, including the area behind the liner.The National Fire Protection Association (NFPA) recommends that chimneys be swept at least once a year for fireplaces that are frequently used. If you only use your fireplace on special occasions, than sweeping every 2-3 years might be acceptable.
It is important to consult with a certified chimney sweep to set up the optimal cleaning schedule for your specific fireplace usage. They will also take other important factors into account such as the type of wood you burn and the condition of your chimney liner.