The Last Jedi is expected to be the biggest adventures in the Star Wars saga, and in regards to length, it is the biggest. According to Cineworld, the official running time is 150 minutes and pushes Attack of the Clones of 142-minute runtime out of the top spot.
Considering the length of two-and-a-half hours, it is possible that the film website has estimated an expected time, but with Rian Johnson having announced that post-production on the film has completed, the runtime has credence.
The original 3 movies in the trilogy are the 3 shortest, with Star Wars, The Empire Strikes Back and Return of the Jedi at 121 minutes, 124 minutes and 132 minutes. It is possible that with the movies being made when the saga was not a dominating pop culture force, the filmmakers had aimed to have a trim production.
By the time prequels rolled around, the legacy was established, and allowed Lucasfilm to explore narratives they desired with The Phantom Menace.
Lucasfilm kept a tight lid on releasing any information to the public on the sequel, which opens in less than 3 months. One trailer debuted this year, and a behind-the-scenes reel was released this summer.
Earlier this month, Mark Hamill had responded to a fan who had asked when the new trailer would debut and Hamill said they should tune in to Monday Night Football on October 9.
While not an official confirmation, Hamill deleted the tweet, because he gave away more information than Disney was willing to share.