As has been stated repeatedly in other threads, the ONLY way to determine if fermentation is finished is to do hydrometer readings.
I have a batch of Deception Cream Stout currently in secondary. It seemed to have gotten stuck, so I warmed the room up a bit [67°F to 72°F] and GENTLY stirred the liquid. Without so much as ONE bubble in the airlock, the specific gravity dropped FOURTEEN points in about 24 hours. I think this strain of yeast needs to be called STEALTH yeast!