duration of insufficient life

Hello,
I have no particular comment on the effectiveness of these brushes DiamondClean, except that, as expected, I do not have whiter teeth it is 1 month! :)
By cons, they are exhausted after only 3 weeks with 2 2-min daily.
at that price, I expect that they bring me a more relative to conventional brushes: this is not the case, and it is even the opposite!
still a fine example of misleading marketing: 10% more for 50% in less time ...
I then returned to traditional pro-brush and result in history, there will have a winner: Philips!