SHELF LIFE.  The thickener type, the consistency of the grease, the manufacturing method and the formulation complexity affect the shelf life of grease.  Generally lithium, lithium complex and calcium sulfonate greases remain stable for a long time.  Aluminum complex greases tend to set and harden, but remain stable.  Bentone greases tend to soften on aging.  The shelf life of stable greases (NLGI #0, 1 or 2) is five years while softer greases and other less-stable greases have a shelf life of two (2) years.