One aspect in the practical application of LED phosphors is the appropriate optimization of activator concentrations since this balances phosphor absorption and emission with potential efficiency losses at high concentrations. In this presentation, we discuss this balance with respect to Ce³⁺-doped LED phosphors as well as Mn⁴⁺-doped complex fluorides, specifically the TriGain K₂SiF₆:Mn⁴⁺ phosphor made by GE. These examples point out two separate cases where aspects for concentration quenching can be related to inherent properties versus those that can be addressed by improved phosphor synthesis and processing. Finally, we discuss how concentration quenching can be described using existing literature models along with practical implications.