I now use the Extreme Sill Brush for all my maintenance washes and most of my first washes. I haven't been using them all that long, about four months at a guess. I haven't found any problem with them not lasting. I've seen no significant deterioration or damage so far. The thing is I'm not hard on gear. I allow the bristles to do the work, rather than trying to wear a hole through the glass like I've watched some other operators do. I use heated water, 60-65c in the tank, up to 45c at the brush.I’m interested in the xtremes purely because of the light weight but read they aren’t as long lasting as a lot of the other brushes. Would you say that’s right in your experience?