So you just cracked some glow sticks and you decide you don't want to play with them for very long.

Instead of throwing them away, put them in your freezer. The next time you want to play take them out of your freezer and run them under extremely hot water and they will get bright again. They wont be at the peak of when you first cracked them, but it's a lot better then letting them go to waste.

I would say that that the faster you use your glow from the freezer the brighter it will be, but if you leave it in the freezer too long, the glow will eventually fade after several weeks.
Have fun!