I see a lot of teams with a 2 score or more lead do this, get very conservative. It absolutely drives me nuts when the Packers do it. I will say that often it does work out in their favor, but makes the game a lot closer than my heart wanted.
Here is my biggest pet peeve with the "conservative strategy". OK, fine, you decided that there isn't enough time for the other team to stage the comeback, then fricking milk the play clock to as close to zero as you can when you have the ball. Teams seem to only really go hardcore after the game clock, when there is under 2 or 3 minutes left. Yesterday, after the Packers went totally conservative on offense and I think had a 3 and out, Whelen snapped the ball with like 15 seconds left on the play clock.
Clock management is an art form. Maybe it is easier when you are a fan sitting in your recliner? However, with all the money these teams have, I would be happy to sit in my lounger, up in the Packers press box, and communicate my clock strategy to MLF.