I actually remember the history. I believe it was May 2012 because when it changed (if memory serves me correct - I remember I was doing a B2B2B with my Mom). The shows used to be longer. There had been a lot of complaints on the larger ships (Crown, Ruby, Emerald) because people couldn't get into see the shows as they didn't increase the size of the Theatre when they built these ships. The Royal Princess was going to debut in the next year and they were concerned about the size of the theater on that ship as well. So they came out with the brilliant idea of doing 3 shows per night at 45 minutes. So on one sailing we had longer shows and the next sailing, it was shorter (and seemed confusing after seeing the longer shows and then seeing the shorter shows).
Then, they dropped the 3rd SHOWING of the production shows. So they are back to 2 shows.
I remember sitting next to the CD at the most traveled lunch and he said "It would be best if they just built larger theaters".