Your jeans will have to be washed eventually. When? Anytime from the sixth-month to the one-year mark, when you’re satisfied with the level of fade and marks that have characterized your jeans. The thing about raw denim is, indigo dye will be lost with each wash, so you’ll want to wash them as sparingly as possible.
A bathtub filled with water and some color-retaining detergent is ideal but again, if you don’t have one, the alternative would be to turn the jeans inside out and wash them in the washing machine separate from other clothing. Hang them up to dry and never put them in the dryer.