Is it possible to inspect a chimney flue from the fireplace to determine whether it needs cleaning? Maybe with a flexible shaft camera? What is the procedure?
Of course if you can get a camera up (or down) the flue then you might be able to see excessive build up of carbon (etc.) deposits. However, it will be as black as can be up there and the small light on most USB type endoscopes might not be bright enough to really make an accurate assessment.
Generally, if you're thinking the chimney might need cleaning, it needs cleaning! Chimneys are usually cleaned on rotation by time, i.e. once per year. If you're a 24/7 wood burner through 5 month long winters, then twice a year might be needed.
If you're an occasional fire burner, the flue still needs regular cleaning, because occasional fires don't get the flue hot enough to burn off small deposits. In fact, a little used chimney can be more of a problem than one which is screaming hot every day.