An Apple battery expert told how he thinks it should be done. Use the battery down to about 20%. Charge it back to about 80%. Once every few months (I think he said around three months), charge it to 100%, drain it completely to where the phone shuts down, and charge it back to 100%. He said this "informs" the system with the battery's performance limits. Then, go back to the 20% to 80% pattern.
Turning off LTE voice calling can save a decent amount of battery if you don't experience poor call quality.
Settings->Cellular->Cellular Data Options->Enable LTE->Data Only