Very interesting topic. Especially when flying multiple sectors a day, a standardised briefing tends to become routine and who can really say they're still listening 100% after the second one
Forty years ago I was jump seating in an F28 of Ansett Airlines of West Australia. The airline had very few destinations and each leg was over arid desert lands of the aborigines and not one blade of green grass to see for a thousand miles. The airline SOP required the captain to brief the first officer at top of climb on crew actions required for rapid depressurisation and emergency descent. The first officer must have heard that same brief a thousand times as he had been with the airline for many years.
I watched and listened carefully from the jump seat as the captain started his spiel. First he turned his head to look outside his own side window at the desert below and in a bored expressionless voice started with "In event of a rapid depressurisation, we will don our oxygen masks and ensure communication. You will call ATC - I will do this - you will do that etc etc " as he went through the entire planned drill which took about 45 seconds of him talking while still staring into space outside his side window.
As soon as the captain started this robotic talking the first officer looked at me and winked then proceeded to make faces and waving his hands around and generally behaving like a clown while giving the finger to the captain's back. . With exquisite timing borne of long experience until with a few seconds to spare before the captain was due to turn around and say "Any questions" the first officer was back in position looking straight ahead in studied monitoring of his part of the flight deck. "No questions, Captain" he said. . The captain with his career long seniority within the airline union didn't have a clue at the charade that went on during his SOP briefing . I treasured that scene for its hilarity. Unprofessional? Of course it was. But brought on by the hours of soulless flying over that part of the Australian landscape only the dingoes, kangaroos and red-back spiders would love..