Most scents that use actual urine in them have a date on the package or bottle. If unopened they should be good until that date. I have heard that you can reseal them with candle wax on the cap and then frezze or put in the fridge...but I am not sure if that will be as good as fresh stuff come next year. I did that with a half bottle of Still Steamin by Scent Sheilds...I'll see how it smells next Nov.