HOW LONG SHOULD A US FLAG LAST?   

There is no definite answer to this question.
 

How long any flag last depends on the weather, its location, airborne contaminations
and how often you fly your flag.  Remember, your flag is a piece of cloth that works
very, very hard.  Throughout its lifetime your flag shakes, trembles, drapes, snaps,
chafes, bakes, freezes, ripples, flutters, furls, twists, flaps, strains, flies, unfurls and hangs!
Is it any wonder that a flag that flies continuously needs replacing two or three times a year?
Wind, water, sun and carelessness are the major enemies of a flag.  No one can control
the weather but you can take some important steps to lengthen the life of your flag.
Occasionally washing your flag in warm detergent water will prevent pollutants and dirt from
weakening the fabric.  Always let your flag dry thoroughly before storing it to prevent mildew
or color transfer.  At the first sign of fraying, have your flag repaired before further
damage is done.  Always keep your flagpole as clean as possible and keep trees trimmed
or move your pole if your flag does not have adequate room to fly unobstructed.