TeachMe;
Perhaps flight crew subconsciously coming to rely on cabin crew for that final check instead of triple checking themselves?
No, I don't think so. That's not the way "routine" works, at least in the operations I have been familiar with.
First, cockpit crews will (or should) never, ever rely on CC's word on a safety/operational matter requiring a cockpit crew decision without that crew checking for themselves. Nor would any cabin personnel expect such!
As I mention above, training covers a number of these issues. In annual recurrent training, we trained front and back end crews together for half the day and despite the usual grumbling, it always seemed a good day and we learned and reinforced learning. The sessions are really valuable because, often for the first time, (because of differing annual scenarios), they learn what we do in an emergency, (and why it may take a few moments before we get on the blower to inform the crew and passengers why we rejected the takeoff, or shut down an engine, etc).