Fireplaces should be inspected and/or swept once a year to prevent fire damage and to keep your home safe.
Like your mother always told you, you don't ever want to play with fire.
To be sure that all of your systems are in working order and operating as they should, it is recommended that homeowners get an annual chimney inspection. The specialist will generally open and adjust your damper, caulk the flashing on the roof if needed, and clean & adjust the fireplace screens & doors. They will also generally check the condition of the chimney spark arrestor and clean the fire chamber. Most chimney sweep companies will put you on an annual inspection plan once you work with them. During this inspection they will tell you if it's time to sweep. Many homeowners opt to have a chimney cleaning done every year as well at this time, especially if they use their fireplace on a regular basis.