I have seen him release just walking halfway in the room. Also, the entire strike takes maybe 8 minutes. (I pop a wax as we are about to start, usually have 1.5-2.5 minutes left) I doubt clearing the room before releasing him (when the room will just fill again anyway) makes it quicker. and if you sit in that one room the shrieker would spawn and wipe you out. If you want to be a jerk, run back up the hallway some and phogoths health regenerates. ;)