Your advice of 110 to 120 pages for script length agrees with what others say, but upon sampling a large number of films I find their lengths usually fall between 85 and 115 minutes, including five minutes of credits. At a minute per page, something doesn’t click. Do producers expect 15 extra pages because they feel scripts usually have fat that needs trimming? Or perhaps producers know that during script development, writers find it less distressing to eliminate scenes and hope no one notices, rather than turn them into something far removed from the original vision. Just a thought.
It’s true that a lot of movies clock in at 100 minutes or less, and that the one-minute-per-page rule of thumb really depends on whose thumbs are doing the measuring. Moviemaking is more art than science, so it never holds up to much mathematical scrutiny. Whatever the reason for the discrepancy, I assure you it doesn’t come from producers trying to spare writers’ feelings.
One variable that really effects running time is pacing. GO was about 102 minutes long. The script was 126 pages, and almost nothing was dropped. The movie never dawdled, however, which is how it got the story told so quickly.
Even movies that end up at 85 minutes probably began as screenplays in the 110 to 120 page range. In the course of production, or post-production, scenes often get cut. Either they are never filmed, or they end up on the cutting room floor, just waiting for the DVD version.
Since scenes are going to get cut, why not just start out with a shorter script? It’s not a bad question. In television, where programs have to be delivered to the network at a precise running time (at ABC, it is 42 minutes, 20 seconds for a "one-hour" drama), it is obviously preferable to avoid shooting scenes that couldn’t possibly fit into the allotted time.
In terms of features, however, anything shorter than 100 pages "feels" too short. It’s literally just not enough pages in your hand. And if you go much beyond 120 pages, people get nervous. Even if it’s great, it feels long.