You can't save a glow stick. Oh, I've tried, believe me; saved them up for a night that I'll just 'know' that this is the time to light up my world. There is no such time- no perfect moment when you just know that you need a light, you get the glow stick, open the packaging with that notch (because they know people like us, and when we really need to open something it takes lifetime, 'cause our hands are trembling and shaking and sweating- they know us and we need serious help), sliding the top off in a grated, apprehensive, almost reverent way. The package would crinkle like candy as you'd slide the glow stick out, rub your fingers over the smooth tube and -crack- a light spreads. That never happens- or it does, but then you realize the glow stick is faulty. Use the glow stick the moment you get it (don't worry, you get another one), even if it's morning, dawn or afternoon. It's not a waste, not a sin, I promise. It will light up all the same.