Do you shock only when you have combined chlorine or do you shock weekly like the pool store people suggest?

This is the first summer that I have been using pool forum and I have been running my cya at 60-80 and FC about 5-6 as per the "best guess chart". I used to run FC at 2-3 and frequently had combined chlorine which I would shock but since increasing my targeted FC I haven't had any combined cholorine.

30,000 gal SWG gunnite pool.

Steve