Wash it when it gets to be stinky or re-colored. It resembles washing your most loved jeans/pants - toss it in chilly water with some cleanser (no sanitizer). When it leaves the wash, you can give it a decent couple of shakes and hang it up to line dry. On the other hand, toss it in the dryer on a low temp in case you're eager. Your pleats are intended to hold up a seemingly endless amount of time. On the off chance that you like your pleats firmer, take your kilt to the laundry and request that they do a "Press Only" Your pleats will look like new.