On the Internet's Screenwriters Listserv, there is often discussion about this form. One of the more interesting follows (anonymously):
The seven-act structure is the standard for "2 hour" films (MOWs) made for American commercial television, which have breaks for commercials roughly every 15 minutes (a TV film of this type is actually 94 minutes long - commercials, station breaks, trailers, etc. fill out the timeslot). To a degree, there are only three unique elements about this structure as compared to features:First, unlike a feature film, the 94 minute length is invariant. From the writer's point of view, however, achieving this precise running time will be handled in part in editing and is not just the writer's responsibility. While there are no hard rules, first draft scripts are commonly 102-105 pages in length (it should be at least 94+) and even the production draft tends to be a few pages longer than necessary to insure that the finished film does not run short. Except for the number of acts, the format of a teleplay is identical to that of a screenplay.
Secondly, an MOW is typically shot on a shooting schedule of 18-21 days, at the rate of about 4-6 pages a day (compared to 2 or less on a full budget feature) and on a smaller budget (obviously some independently financed features or low budget films can have these constraints also). This requires fewer set ups than in some features (remember that the film will be viewed on a small screen and thus scenes in medium to close shot tend to predominate) and some care in not using too many expensive or complicated action sequences. This is not to say that all crowd scenes, long shots, etc. are forbidden - it's important to give the story a sense of place, proper scale, and movement - but there are limits.
Thirdly, there is an expectation that each act (i.e. before each commercial break) end on high note if possible to hold audience attention through what are essentially frequent intermissions. TV films are seven acts instead of eight because, by convention, the first act is allowed to be longest, i.e. perhaps 18-21 pages long, to get to what, for those who like structural paradigms, Field's would probably call Plot Point I, or, more generally, to give the story time to define itself, ask its major dramatic question and build sufficient interest before the first ads appear.
Subsequent acts are shorter and of roughly equal length, though an act may vary by a few minutes of length to accommodate the need to end an act at a strong moment. This is particularly stressed at the end of Act III, which is the midpoint in this sort of structure and comes, again where feasible based on the logic of the story, at the end of the first hour when the audience has a whole new range of other program options.
Actually, if you read someone like Syd Field, and locate his plot points, mid-points, and pinch points, and think of these as coming at the end of each act, you have something very much like a seven-act structure layered over the conventional three-act structure of feature films. In that sense, an MOW is similar to a feature.
There is room for disagreement that the transitions need really meet Field's definitions of his "points", but clearly, the TV film does strive toward strong transitional moments as act breaks. And again, these "rules" are flexible to an extent to accommodate the logic of the story.
Since MOWs need to do this by convention, or else lose its audience at intermission, they are a good form to study for plot points and moments of heightened interest.
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