I've only ever cooked 3 briskets, all of them British beef and messed only one up and that was due to operator error. The trick is to do just what takingthebrisket says and have a skewer or tooth pick on hand and make sure it goes through like butter. In my experience (which is limited) the meat has been around 203-205f at this stage.
Once it's cooked, we just slice off what we need then break it down into large 2 meal chunks and vacpac it then reheat in simmering water or water bath till it reaches a safe temp. Nothing beats leftover BBQ