In the old days it was a bi-yearly maintenance chore. But I've let it slid a bit lately as I've only put about 1000 miles on the car in each recent year. I know that time as well as mileage is a factor, but when I flushed the brakes this time, the fluid was remarkably clear. Not that dark, water-sotted color it used to be. Maybe the fluid is better today. I've installed speed bleeders on my motorcycles in the past, and like the convenience (kind of a built-in check valve). So maybe, in two or three years when I get around to this again–I should live so long–I might give you a buzz and pick up the eight required for my front and rear Girlings.