The shelf life of all STA-BIL products is 2 years after the bottle has been opened, provided it has been tightly capped and stored in a cool, dry place. If the product has not yet been opened, you should use the color of the fluid as an indicator. If the product is still bright red, it is fine to use. If the product has turned to av ery dark red (or brown) color, we recommend purchasing a new bottle. It will not harm anything if you use an old bottle of STA-BIL, it just may not be as effective.