All items have been washed a couple of times in very hot water, and dried using heat to set the dyes and pre-shrink the fabric. This is why I always include height and width information with my shirts; they might all come from the same manufacturer, but they all shrink in their own unique way.
Washing your items in cool or cold water, and line drying them, will help keep the colors vibrant longer. That being said, there's something sweet about a tie dye softening and fading over time and use. Like denim, tie dye only gets better with age!
Please don't use bleach! You knew that, though.