Many years ago when I was in college, one of my professors wrote a Star Trek Next Generation script, and she talked about how the producers pretty much destroyed her story by insisting she stick to the formula such as "between X and Y minutes, the Enterprise or one of the main characters must be in danger. That danger must be resolved by minute Z." Sigh.
>>techno+(OP)
Since not every episode follows that formula, I wonder if that's a requirement specifically of spec script writers because they'd want to keep the more important/interesting episodes written by staff.