Another bunch of bullpie... "Defensive driving school", "insurance companies"... same entities that recommend using "wheel shuffling" exclusively and keep your hands at 8 and 4 o'clock - now that's a sure way NOT to be able to handle an emergency situation. I'm getting more and more convinced that most of this "education" is designed for complete idiots - who should not be behind the wheel in the first place!
"Checking over your shoulder", when done properly (checking the mirror in the process) takes below 0.5 seconds (I consistently do it under 300 ms) - that is less that 15 meters (45 ft) on highway speeds. That is still a non-negligible distance, but without convex mirrors there is no way you can afford not to look during lane changes.
1. I'd really like to see your credentials. What driving school do you instruct at? Is it Bob Bondurant? Maybe Russell Racing School, or possibly one of a nice list of high performance driving schools. In order to speak from on high, most certainly you must be a professional driver with the licensing and credentials to back up your high and mighty status, right?
Bob Bondurant teaches the 10-2 and 9-3 steering position depending on the course you're taking ... but you obviously have better credentials than he and his staff have.
2. You try to pass yourself off as better than anyone else here, because you can supposedly check over your shoulder so fast...and you have to brag about how skilled you are in this facet of driving. I'd love to know when your stopwatch starts and stops, especially considering that you're working to focus on something so quickly, process the information your eyes receive and act on that information... which can change quite easily by the time you've started your movement into the other lane. Besides, if you're TRULY an advanced driver (which you claim to be), you would be aware of your entire spatial area surrounding your car at least one lane on each side, and have an instinctive reaction to any situation in which you might find yourself making an emergency maneuver. You should know that. One space in all directions, like you're the center square on the face of a Rubik's Cube (instructor used this reference). If you are truly aware of your surroundings, then you're only using your mirrors as a double check to make sure everything is where you already know they are.
I prefer to be able to look into the mirror as I start my lane change, which eliminates people from two lanes over changing into the spot I've picked out. It's happened before, and I'm able to catch them from wherever they are when they do, so as not to hit them.
With my mirrors set the way they are, I can see one lane to the left, one lane to the right, and directly behind me with the interior rearview mirror. Continuous coverage without any spot for even a motorcycle to hide in...
20+ years of driving, one non-fault accident where a woman pulled out in front of me with less than one second to react, I was able to avoid colliding with her (potentially killing her), and no other accidents on my record. Well over half a million miles of driving...
...and your record?