I keep it refrigerated, and I am hearing a lot of different answers. Some say only 48-72 hours, others say longer. I'm using the sterile water in the vials that comes with the kit, but my buddy says I need some type of special Bio-static water that allows the molecule (sp) to last up to 28 days?? Now, since I'm only doing 2iu's a day, thats nine days for each vile. I hope my shit is still good.