My opinion only: I have plenty of drills available that involve a time standard, and dot torture is not one of them. I have never put a timer on myself on any of the dot torture strings. The only thing I do is make sure I am not turning it into a bulls-eye session. I use the whole drill almost like the first dot on the press six drill: working on braking the shot right as I get to extension on a draw, or as soon as the front sight returns to the dot I am aiming at, without adding time pressure. That comes in my practice sessions, just not with dot torture. Once again, just my opinion and personal way of practicing. I am sure others use a timer, and also get a lot out of it.
Usually I do dot torture as a warm-up, a few times I have done it as a cool down, but not for some time.