Just out of curiosity, I tracked Vikings/Bears today.
2:30 media timeout after every possession, with two exceptions -- late in the 2nd qtr (one play after the 2-minute earning), and late in the 4th (on the last turnover).
With quarter breaks, that's 18 timeouts of 2:30 each for a total of 45 minutes, plus a 13-minute halftime (for a total of 58 minutes). They also did two split-screen :30 breaks on team timeouts.
Big 12 games have 16 breaks that total somewhere around 50 minutes, plus a 20-minute halftime (for a total of 70 minutes).
That 12-minute difference just in media breaks and halftime makes up most of the difference between college and NFL game length.