My FAs today were very aware of the free drinks. They sat for the first 45 minutes, then had a "water service only" for the remaining 45 minutes.
I've had this happen before. The captain was clearly in on it, saying he expected turbulence that never showed up (despite the cloudless skies--smoothest ride in weeks).
It's getting as predictable as the FAs telling everybody to pack up 30 minutes before landing on the last flight of the evening.