Today an average porn scene probably runs 30-40 minutes and the actual intercourse (i.e. excluding tease and foreplay action like oral) is maybe 20 minutes
The scenes that run 30 or 40 minutes or even longer are great for when the girl is one one of my very favorites, but with girls that I like but don't love
With scenes running 30 to 40 minutes, there's plenty of time to run through different paces and pleasure for each of the participants as they trade off
tell ya: I like it when there are more scenes and girls on a "director's cut" DVD -- 6 scenes is a good minimum number, or even 7-9, and some could run 30