Sand Fisher:
Interesting. Sadly drivers fall into two camps those who seem it beyond them to accept being flashed in the “I know how long my truck is brigade” versus the “Let me know drive when you are happy with the distance”. I am in the latter camp. For what it’s worth with no flash when the overtaken truck is about 1/3 down from the top of my n/s mirror is when I would come in. There are of course drivers who feel it is beneath them to flash in at all.Flashing important at night and when it’s raining. Rain droplets can be a bugger on mirrors.
Ah yeh, the… ‘‘I don’t need flashed, as I know exactly where the back of my trailer is’’ crew 
, usually the ones that contradict themselves every time they (nearly) overtake every ■■■■. . arse wipes of the highest order. 
I’m in the same camp as you, but tbh I couldn’t give a toss if I’m flashed in or not, if I am fair do.s, I always think they are a decent considerate driver, not a twunt, …but if not I always leave more space than I need to before I pull back in whatever.