Depends on the project. Most, though not all, films run about 90 minutes in length. By the standard 1p=1m guideline, that is about 90 pages. It's inexact so the actual page count can vary from 85-100. For some genres, the theatrical film run time is 2 hours and occasionally 2.5 hours. Then the scripts tend to be 120-130 pages. For television, time must be allowed for commercial breaks. So an hour program can actually be 45 minutes long. Most hour tv scripts are about 50-55 pages. So generally a script written between 90-110 pages is an ideal range for feature scripts adaptable for theatrical or MoTW television release. There will always be exceptions.
If there is a specific limit placed by a festival, contest or production house, that must be observed. Otherwise, there is no specific rule how long a feature script must be. The longer it gets, the higher the production costs and the more taxing it becomes on the audience. However, for theatrical release, most production studios and theater owners want to turnover seats. So a 1.5-2 hour window (90-120 pp) is dominant. With more media being delivered in home (DVD, BluRay, VOD, cable, etc.), it will be interesting to see what effect that has on the length of original content. Given 'netflixing' maybe sitting through a six hour narrative will be reasonable if it's at home in your pajamas. While in a theater probably not so much.