Welcome to the industry I guess
Though I don't have any first hand experience it does sound absurd. Then again I'm talking from the perspective of someone who's attention span generally hits rock bottom after four hours of anything.
One thing I do know is that generally people don't perform better/faster when they work more than say 8 hours a day. There's plenty of research to back that statement up on the web so perhaps you can use those 4 extra hours on a 12 hour shift to find some good arguments to plead for sanity with the producer?
The cats are watching us...