Do you think it's because of a lot of scoring, a lot of incomplete passes, or a lot of penalty enforcement. The first two probably have the biggest impact to length of game. I don't think you'll see a huge difference either way in game length with the 40/25 clock. We didn't track that closely before and after, but we have been about the same game time anecdotally. We have tracked game time the last two seasons for our crew and it was 2:20-2:25, and we had several games under 2:15. The other big time killer is getting out of time outs efficiently and change of possession/score. If you clock these you'll find many of them are 2-3 minutes. If you can consistently make those 1 minute you can cut at least 10-15 minutes in game time.
In my opinion...here is the evolution of long games since on or about 2002:
1 - Scoring has increased: frequently, there's either blowout games (that do not meet the criteria for a running clock), or games in excess of 60+ points scored between the two teams.
2 - Incomplete passes have increased: I just looked up stats for a state finals game. Combined the passing was 27/53..or 26 incomplete passes..or time standing still for these plays until the next snap.
2A - Turnovers have increased: a byproduct of more passing. Or time standing still for COP.
3 - Increased OOB. "back in my day" I never saw Walter Paytin, Barry Sanders, Lynn Swann, etc. dash for the sidelines v getting an extra yard. Nowadays, a player (emulating NFL/NCAA) sees a sideline they're running for it. More time standing still.
Not so long ago, when black pants replaced knickers and folks were communnicating their displeasure...but eventually liked the idea of the black pants, it seems the game' rules regarding timing can also evolve to consider the time involved for these contests (at a HS level no-less).
For several reasons, the NFL, and FB overall, has lower viewership. It seems somewhere on this list of reasons is that folks do not want to sit through a 2.75-hour HS game or a 3.5-hour ncaa/nfl game.
While i'm no fan, for the most popular sport in the world, soccer, games are 2-hours long--even including stoppage time.
A few weeks ago, Manchester United played Manchester City in a regular season contest with nothing "on the line", yet 600 million world-wide was watching. or about 500% more than sees the 4-hour long super bowl world-wide.
The most popular form of racing, F1, has races that are never longer than 2.5-hours...and nascar wonders why viewership is down. Each week, F1 has more viewers world-wide than the "super bowl of nascar"--the Daytona 500.
It would seem reasonable for the football powers that be to look at the big picture and review items 1-3 listed above and do something to get these games moving.
Goodness, I would favor (NFL/NCAA) 25-min running clock quarters (100min) with 'normal' timing the last 2 min of each half. Toss in the normal 20-min halftime. Rarely would we see a game in excess of 2.5hr.
HS would be 20-min running clock quarters and games would be about 2 hours.