At what time should I start checking for the halftime show at this years' Superbowl?

I’m not a sports fan, and I will not be watching the Superbowl. I do however want to see the 2 1/2 minutes of 3-D commercials that are supposed to air right after half time. I know half time is whenever the game is half over, but not being someone who pays any attention to how long a Superbowl game usually takes, or what time a half time show usually comes on, I have no idea when to start perusing the channels. What do you think is the best time to check where I won’t have already missed it?