Sorry if this is something you know.. but sola suggested taking one to see if/when it's finished. So, yes take one now.. that will be a point of reference.. take another in a week at the same temperature.. compare.. If it's the same.. you are done.. probably.. but, with a stout? I'd leave it and take another a couple of weeks after the 2nd one.. Sure won't hurt to let it sit for 4-6 weeks in the primary... even longer before bottling.. Probably improve it a lot. Easy to get antsy.