I try to rotate out my tubing once in a while, usually when I notice them getting hard and not flexible. Other than that they are stained by iodophor quickly, after that I don't even see the oxyclean haze.
In Primary: Belgium Chimay clones.
In Secondary: Braggot, pale ale, end of the world white.
Conditioning: Mead, Cider, braggot, Belgium Wheat.
On Tap: Clones, Chimay Blue, Red, Porter, malted cider.
Bottles: Far, far, too many to list.