@rambo62,
You're missing the whole point of the game. The easiest way to 'run out the clock' is to keep possession of the ball by making first downs. The only way to make first downs is to move the ball forward ten yards in four downs.
No team ever runs around in their own backfield in an attempt to 'milk the clock' because it wouldn't make any sense to do so.
Far better to take all the time (40 seconds) between plays and run the ball forward. In the scenario, you're envisioning, let's say there one minute left on the game clock. A team won't take the chance of getting caught for a loss by running backwards, they take the 40 seconds, run a play, (usually take a knee) then wait for the clock to run out.
BTW the average play in football is closer to 10 seconds or less.
Joe(Good luck tomorrow)Nation