Coolant Flush

How often is a coolant flush and fill recommended? My radiator is still in good shape (no deposits on the inside yet) and I just did a Prestone back flush on it last year. Should this be done annually, or should I wait until the coolant starts turning color? Thanks!
Matt

Most recommend doing it yearly.If the coolant turns color its too late.
Wayne

I drain, back flush and refill with new coolant, it also gets a new pressure cap. I also now clean all my grounds ever since I found out that bad grounds can cause electrolysis inside the radiator resulting in a plating effect from any minerals in the coolant.
For extreme build up [how to do you look in the rad to see if its clean, you got some kind of periscope or something ?? ] I recommend the prestone 7 hour flush, stuff cleans like the proverbial white tornado. Use distilled water when refilling. I would like to find a way to use distilled water when I backflush the system so I know I got all the tap water out from the garden hose.