That is a long time for a fermentation to finish. I would check it a couple times over a two day period and if no change is noted, then rack it off the lees to its final packaging (but if a change in gravity is noted, I would give it a little more time, if bottling, or just rack to keg, if kegging). Other than sours, I never go 6 weeks in the primary anymore (but I have a Tilt to tell me when no gravity changes are registered).
Good luck with your Chocolate Stout.