Even if you do the weekly or daily commute on the same type of a/c, it makes sense to listen to the safety brief.
The cabin configuration may be a little different to that last "same" a/c and the brief will focus the unconscious part of the mind on this fact, lessening regression to prior experience "I'm sure there used to be a door here..."
The other point is that the flight attendants deserve the courtesy of being treated politely and passengers staying "heads down" when they are trying to do a professional job is very rude IMHO.