I am obsess with Colourpop eye shadows, aside the wide range of colors and affordable price 5 USD (Or around 90k IDR in some OS), we are addicted to bouncy feel, Smooth texture and how pigmented these shadows are. In the application tips section (on the bottom of the page), they told not to forget closed the lid tightly to make sure not to lose the magic that make the shadow feels amazing.
If you have bunch of Colourpop eye shadows, you won't have much time to twist the lid tightly to make sure none of magic (or the secret ingredient, that make the eye shadows amazing, dry up). Store them in air tight container, You could easily find one and they are totally affordable.
The air tight container that I use is Biokips, you could buy it at Ace Hardware. They often held up to 50% sale, so each container would cost around 17k IDR to 50k IDR (2 USD to 5 USD) according to the volume.