The final minute of the fourth quarter lasts five and a half minutes on average. The median length is 4 minutes. At the extreme end, the November 18 game between the Nuggets and Thunder featured a final minute that took twenty minutes to complete. Those last 60 seconds featured two official reviews and a plethora of free throws (12 in total) as the Nuggets repeatedly fouled the Thunder in an unsuccessful attempt to stave off defeat. In the pre-shot clock era, the NBA apparently found late game hacking to be rather unseemly and instituted rules to discourage it. In the final three minutes of regulation, made free throws were followed by a jump ball, rather than automatically awarding possession to the fouling team.
Because why not. The chart below summarizes game length by broadcast network (another readily available field in the stats.nba.com data). As you can see, with the exception of NBA TV, nationally broadcast games take 15 minutes longer than local broadcasts. The extra length is presumably due to additional commercials. An examination of the detailed data verifies this presumption, with the biggest gap in length between national and local broadcasts occurring when NBA rules require mandatory timeouts.