As a cast member doing cross-u (temporary assignment during busy times) many years ago, I sold a lot of those things around World Showcase. The ones we sold were either green, red, or blue and they only lasted one evening.
One of us would have to stop by a warehouse (back of China, somewhere) and sign-out a cooler (or two) filled with the things. They were issued out of a deep freeze (-30 below zero, as I recall) a couple of hours before sunset. We were told they were filled with a microorganism - plankton or something - that would only glow for a few hours after the tubes thawed.
So I truly don't understand how a comparable product could be purchased days in advance and not stored in cold temperatures.
Please note, I'm not saying anyone is lying; I just think the product sold at discount stores has to be something different. Maybe something with a chemical reaction rather than plankton (or whatever)?