Update.
Mother in Law lives bang straight across road so thought I'd try it out on hers seeing as mine are totally clear.
From leaving my back door, getting tackle from garage and taking it across road to back of hers, setting up and cleaning an 8m length of moderately soiled gutter took..................7 minutes 38 seconds.
This was on a bungalow....the entire length was filled with at least an half inch of dried soil/moss.