You don't ever need to shock unless you are fighting something in the water. You will know if the water turns cloudy, or if you have any combined chlorine. Sounds like your chemical numbers are right in order. If you make sure that you don't let the chlorine get low enough for anything to start up in your water you should not have to shock. As for using a metal sequestering agent, if you see any stains start to form you can put some in. Staining means the sequestering agent is too low to keep the metals in suspension, so you need to add more. I don't use a maintenance dose, I just add when I see some discoloration starting on my pool. Let us know if you have any other questions, Happy swimming!