I work in smaller time scales professionally… :30 seconds, 2-5 minutes, 7-10 minutes.
The way I gauge how effective my work is on the small time scale is if a non-professional feels like the work is short or too long.
If I get a “That felt like 3 minutes” when watching a 7 min piece… then I feel like I’ve succeeded.
If I get a “That felt like 15 minutes” when watching a 7 min piece… then I need to go back and cut tighter.
Time is such a subjective experience… When I get a call saying “We want a 2 minute piece” – I generally tell them, “No, you want a 5-7 minute piece”
The same has to be with the feature lengths. If not done right an 88 minute movie could feel longer than a 110 minute movie.
I’ve watched movies that can’t keep my interest over the 90 some minutes they’re on, but I’ve sat through 2795 minutes of Battlestar Galatica (not in one sitting)
But on the general, I would say that movies have been getting longer and longer. Call it Directorial narcissism… The creators of the film have the most vested interest in the story and the characters so they want to see the longer cuts.