not really sure, had my original salmon for 2 1/2 yrs and while it's well warn it still seems ok, got the curved look on the sides where it catches and rubs on brickwork. only changed cos i wanted a sill brush, don't know how long that will last as it loses bristles quicker. anyway i would expect any brush should last at least a year. obviously as a brush wears down it'll take longer to do the job.

when you aint got no bristles left