This past week was actually a TEXTBOOK case of why the staff should "always" rotate a backup QB in every now and then, even for a series in the first half. What I mean by this is you can have your starter play 75% of the time, and a backup 25%.
1) Every other position rotates - guys compare notes on the sidelines of what they're seeing, how they're attacking it, etc.
2) Keeps the "backup / 25% guy" fresh and ready should an injury cause him to be the "starter / 75% guy".
3) Keeps the competition alive and, hell, you just never know if you've got a great QB on the bench. (I mean, we can laugh, but look at ISU QBs)
4) If you realize in the 3rd quarter that Stanley's having a terrible day, you let the other guy take over if he looks like he's having an ok day.
I just don't see a lot of downside to this approach... I get that people here will mock the idea, but nobody ever has much of a reason not to do the above aside from "QB is different".