JAL does a pretty good job prepping for the JCAB test. They review every possible question in J-lish, so it took each of us a max of ten minutes to complete. We were told to not get up before 30 minutes, though.
It was funny. Everyone in the room looking around at each other until the 30 minute mark. The gaijin got up first, followed by the Japanese. I think one or two non-JAL took the entire time to complete the test.
Good luck!