I seem to remember a recommendation several years back to use organophosphate tag for three years then a pyrethoid tag.By rotating tags,you won't get immunity to either type of chemical as fast.Personnaly,I never was sure about the combination tags.
Not bashing tags because I still use them on one place I graze but I have had good success with back rubs or pour on fly control like Ultra Bos, Ultra Sabre or Delice.If you can get the cattle in,these might be more economical and give a surge in protection.
It all comes down to your situation,wallet and time.If you use tags,you might want to remove them at the end of their useful lifespan to prevent low residuals creating resistance. My opinion only.