Ok, but I have to assume that the fixed windows for ads are based on some sort of assumed avg game length that’s in the neighborhood of 3 hrs. If college football seriously considered implementing rules that kept a running clock after first downs and incompletions, I could legit see that taking a full hour out of the broadcast.
Its network dependent, but the fixed windows are based on defined stoppages in play, not stoppages per X number of minutes of airtime. CBS has way more than ESPN, which is why their 2:30 game often runs until 6:30 or 7:00 PM.
For example, ESPN’s agreement may be 20 breaks each at 90 seconds, and they would be something like the first 8 qualifying play stoppages per half, plus 4 more at half time. Qualifying play stoppage would usually be a punt resulting in change of possession, scoring play, conventional timeout, injury timeout, or turnover on downs. Turnovers (fumbles and INT’s) typically don’t get the TV timeout treatment.
So no matter how much you shorten the game action itself, you’re never going to reduce the total number of commercials, because all those stoppages are still going to happen. Networks aren’t stupid and neither are the advertisers. They both know where their bread is buttered.