Combining these characters paints a vivid picture: “the old opera role's frequent talk.” The phrase originates from the image of an experienced actor playing an old, wise character who repeatedly delivers the same moralistic lines in a play. While the lines are wise, their constant repetition makes them predictable and stale, losing their impact on the audience.
老生常谈 is a versatile idiom used in various situations, almost always with a weary or dismissive connotation.