HD officially isn't going to instruct anyone to put NS in your refrigerator to avoid legal issues in case someone ingests it, but as long as you make sure the caps are tight (put some tape around them too), put them in an air tight baggie and in a cool place out of the sun you should be fine using it even a year later. I brought home a bunch of opened up containers of NS from last year's SEMA and they are still performing just like when they were fresh. I can't stress to people enough that you need to apply the product super thin to avoid any trouble with removal. Too think and it affects the bonding/linking of the product to each other while it's on the surface. Usually, the only thing that is needed is a damp towel to remove the streaks. Others have had great luck applying a super thin layer of POXY over it to remove it. In extreme cases, a simple wash is all that is needed.