QUOTE(McMark @ Feb 28 2011, 03:51 PM)
You don't need to replace it. Just clean it.
Factory manual called for cleaning every 3000 miles at first, then in 1972 changed it to every 5000 miles, then in 1973 changed it to every 20,000. Finally, in 1975 they dropped it from the maintenance schedule completely.
So I'd say it's up to you. Clean it as frequently as you feel comfortable.
Just don't over torque the attachment bolt. That can really screw up your day!