Tony,

I have taken club repair course and the instructors have always stated the you show have you clubs replace on your play. You may have to replace the shaft. You should replace your shaft every 1 to 2. The materials in the head now break down do to
the ball you play, were you store the clubs( do to hot and cold, Trunk or club storage area) and how you play( Swing speed and contacting the ground{ Hard, frozen})

A good rule of thumb is to the following:
Long hitter or 3 to 5 rounds a week should replace their clubs every 2 years and shafts one a year.
weekend or 1 to 2 rounds a week - every 2 to 4 years and shafts 1 1/2 to 2. Depending on your swing speed and talent.

I hope this help you out.