hi, i do use lots of water,and i rarely get any complaints but it is me that is not happy.
however i monitor my own windows and have noticed that even without rain they get dirty very quickly and it appears as spots even when it is clean immediately after drying.I have cleaned some by hand next to wfp ,and there is a noticable difference after a few days .that is what concerns me if the customers are noticing the same,especially as i have said that the glass seems to have changed from sheeting to droplets.Finally the weather has no bearing as i have been noticing this for quite a while.