Essa é uma pergunta muito interessante. Embora não consegui encontrar uma resposta precisa, aqui estão algumas considerações interessantes sobre o assunto que aprendi enquanto pesquisava.
deste artigo sobre wikipedia :
< p > < .html "> Cinemablend tem um artigo interessante sobre este mesmo tema:A feature film is a film that runs for 40 minutes or longer, according to the Academy of Motion Picture Arts and Sciences, American Film Institute, and British Film Institute, though the Screen Actors Guild states that it is 80 minutes or longer.
The majority of feature films are between 90 and 210 minutes long. The Story of the Kelly Gang was the first feature film based on length, and was released in 1906. The first feature-length adaptation was Les Misérables which was released in 1909.
Feature films for children are usually between 60 and 120 minutes.
There's a school of thought that says 90 minutes is the perfect length for a movie-- the length of 3 TV episodes, just enough time to get in, tell your story, and get out without wasting any more of the audience's time. There are countless examples that prove the rule, economically told stories that feel perfect and tight without a second wasted.
Finalmente, há uma resposta em wikianswers que tem uma visão diferente:
Most movie scripts are 120 pages and a page translates to roughly a minute of film, hence most films being about just under 2 hours. It's quite genre dependent as comedies and animations are rarely more than 90 minutes, but summer blockbusters and thrillers are usually about 2 hours.