I'm a firm believer that testing is a waste of time and money once a tank is established. A reefer with a keen eye can determine the tank condition by observation only. I don't routinely test for anything, observations are a clear indicator of issues.
If you do have a soft coral dominated tank, dosing iodine as per the instructions could be beneficial, and certainly won't have adverse effects if the instructions are followed and routine water changes are performed. Again, coral observation / extension are visual indicators whether dosing iodine is actually doing anything of value, if no real changes are noted, then dosing iodine is probably unecessary, it depends on your water change routine and frequency really.