There are a plethora of synonyms for the term "remain effective" that can help one express the idea of sustained or continued efficiency or usefulness. Some suitable synonyms for this term include "persistently effective," "enduringly efficient," "perpetually useful," "long-lasting productivity," "consistently capable," "durably successful," "chronically impactful," "unwaveringly powerful," "indefinitely functional," and "reliably potent." Each of these synonyms imparts a slightly different nuance of meaning, but they all embody the idea of ongoing effectiveness that persists despite changing circumstances or obstacles. By utilizing these synonyms, one can add variety and precision to their language while expressing an important concept.