When to wash your jeans is a matter of personal taste. But you'll know it's time when they get baggy at the knee or saggy in the seat. Or if you get something messy on them. Here's the best way to preserve the pants you wear almost daily.
For the least amount of shrinkage and indigo loss, fill the bathtub or sink with cold water. Turning them inside out will keep them even darker. If you're looking for a little shrinkage with some color fading, use warm water. Add a small amount of a gentle soap (see below) and let them soak for 45 to 60 minutes, occasionally agitating them by hand. Remove them from the water, rinse with cold running water and hang until completely dry. The less launderings you do, the more individual character your jeans will naturally take on.