Not a musical, or really answering your question...but, reading this made me think about the 2012/2013 revival of "Picnic" at Roundabout. The play is 3 acts long, and usually (at least in productions I've seen have two 10 intermissions between acts. This time they decided to have the first act run about 1:20hrs, then act two was only 30 minutes, with a 15 minute intermission. I thought, I would have given up the intermission and just plowed through.