Why do soft-close seats stop closing slowly after a year or two?

Multiple r/Plumbing and r/HomeImprovement threads attribute this to the damping grease inside the hinge drying out or to plastic hinge components wearing. Reviewers report this on seats from Bemis, Church, American Standard, and Kohler alike, which is why community consensus leans toward seats with metal hinges and replaceable hardware when long-term silent operation matters.