I too am worried that you haven't posted any hydrometer readings. Have you taken any? Otherwise there's no real way to tell when your brew has finished fermenting.
I can tell you that 16 days for an extract stout would normally be much more than enough time to ferment fully, and it's very likely your beer is ready to bottle. But without knowing what gravity your brew is at, and if it's staying the same for a few days in a row, there's risks involved. What if most of your yeast was dead at pitching? What if your fermentation temps were too low and the yeast has been sleeping this whole time?
If for example your yeast was dead or asleep, then you've just got non-alcoholic wort sitting in your fermenter, and you don't want to bottle that!