I went and watched Boyhood yesterday. As you know the “gimmick” is that Richard Linklater used the same actors over a 12 year period to portray the same characters. But actually this turned out to really heighten the verisimilitude. You are used to seeing different actors play the “young” or “old” version of the same character. Though they are roughly physically congruent, they are not the same person, and it shows in aspects of their affect and manner. Often it’s subtle, but in hindsight after watching Boyhood the contrast is real. Using the same actors did produce a continuity of character development which was fresh and new. In addition, specific writing of the script obviously occurred at different points, as there are tells to particular developments between 2002 and 2014. For example, you see the shift from portable land-line phones as the norm in 2002, to flip-phones in 2008, to smartphones in the early teens.
At nearly three hours the film is a bit long, and the later teen years of the main character’s life was less than compelling. Also, the older sister played by the director’s daughter was a bit of an odd fit because unlike her brother she seems so physically different from both of her notional parents, played by Patricia Arquette and Ethan Hawke. That somewhat undercuts the realism which was a structural part of the movie as the characters aged and changed.