So I can't stop thinking about movie run times today, so I updated my post with some new info if you omitted sequels from the data (aka a big thing I suspected was leading to longer films).
It turns out, yes! If you are in your late 30s to early 40s, non-sequels are only 2 minutes longer than when you were a kid (based on my data set). 😱
@matt
Interesting blog entry, although I have no idea what you mean by "prestige TV". Blockbuster rentals?
You mentioned rentals but you seem to have overlooked the rise of cable TV in the 1980s--think HBO and Starz. The shorter films in the 1980s likely were to accommodate additional advertising before the film starts.
There's also a new marketing paradigm in play these days, with the longer films--the objective, I'm sure, is to keep theaters filled by the entirety of the film--so if you wait until the film gets run on TV, you'll get a version that is "edited for content and for time", which is usually the case these days.