I went this afternoon to see the movie Boyhood. We meet Mason at the age of six and follow him until he graduates from high school and heads to college. A fascinating aspect of this movie is Mason is played by the same boy throughout. The cast and crew assembled for about a week each year for twelve years. Yes, that was worrisome for the director (and investors) because something could have happened to the lead actor along the way.
Though the movie is built around that gimmick it actually turned out to be a good story. There aren't worlds to save, just seeing what a boy goes through to grow up. And that seemed pretty real. There were a few story threads that didn't develop, such as when he faced a couple bullies on his first day at a new school.
I wonder how much of the movie was written before filming started and how much was written before each year's shooting. I've heard news stories that the director had a conversation with the actor before the filming started each year because the director didn't want to include things, such as teasing by guys about girls, if the actor hadn't encountered such a thing yet.
The movie doesn't announce the change in years. Sometimes it was obvious – Mason's crew cut suddenly grows out or his mother meets a nice professor and in the next scene they return from the honeymoon. But sometimes it wasn't and I wondered, he does look older, doesn't he?
I think the overall theme of the movie is responsibility. First, there is the growing responsibility of Mason's father – the parents are divorced when the movie opens. Then his mother's struggle with responsibility as she goes through a boyfriend, then husbands two and three. And towards the end we see Mason begin to struggle with it as he flirts while on the job or blows off class.