In my opinion, the brushes deteriorate quickly, about 2months and there past there best but you can carry on with them, and bristles do come out on windows, this makes them expsensive but the most important thing is there LIGHT which is really what we want and as far as im aware there isn't anything better on the market, if there is please say what it is.
If someone can double the bristles and keep the brush head roughly the same weight we would have the perfect brush, we havebeen to the moon so must be possible, cheers.