Agree with DrDawg. Having grown/sold hundreds and hundreds of Peace Lilies, your plant is likely root bound. You have had this plant for 2 1/2 years. When was it last repotted? How many times have you divided the plant? What type pot? Clay or plastic.
Rick's method will work. But if it is pot/root bound, it needs to be divided and repotted. Unlike some plants that don't mind being terribly potbound (e.g. Agapanthus), Peace Lilies do mind.
aboard.
