I will add my bit to this.
I have 2 poles working and have put a dual trim medium on each pole (the white bristles), I also have quite a concern about how long these brushes will last, they seem to be holding shape (just) but have continuosly lost bristles for the 2 weeks they have been in use.
While they clean very welll and do a good job on fascias, I feel that they may not be man enough for the amount of use they get on a 5/6 day week.
If they do not manage to last at least 2 months, then I think I may well have to go back to a heavier and cheaper Vikan, because at £40+ a brush they need to last for a good while.