Mine specifically recommend not to refrigerate them. This is taken right from the instructions:
If you choose to store your Neck Buddy in the refrigerator, please note, you will increase the chance of mold forming, and the Swimming Pool Effect is more likely to occur. The Swimming Pool Effect happens when you first wear your Neck Buddy and your body becomes acclimated to the fabrics cooling, so it no longer feels like it's working.
It also says:
How does the Neck Buddy work to keep you cool?
When placed around the neck, the Neck Buddy lowers your body temperature by cooling the carotid arteries in the neck, and provides an evaporative cooling system for your body to help relieve heat stress.
I followed the instructions that came with mine and soaked it for 5 minutes, and then disbursed the crystals more evenly, and then soaked it for another 25 minutes. I just did it in normal cold tap water. The instructions also say to rehydrate every 3-4 days, and boy was that true! It stayed hydrated for several days and took a long time to dry out. I never had to re-soak it and it has just now completely dried out this week.