I always describe use of mirrors as similar to a video where you are continually aware of what’s happening around and behind you (as far as possible). This beats the general tuition of “check your mirrors before any change of speed, direction and before signalling”.
Personally, I find it adds a great deal of interest to the drive. Motorways, in particular, can be so boring! But start making the “video” and you can track folks’ movements and anticipate their actions. In some cases you can predict a near miss or an accident quite a long time before it happens.
It is by far and away the safest method to use mirrors. It goes hand in hand with the traditional scanning method and is just a different way of describing that.
And, regardless of what some may say, there really is time to look forwards as well!
Pete 