The best care is to hand wash with light detergent (woolite is best) or a tiny bit of shampoo.  And then air dry or put in dryer for 10 min on low heat. It should last a really long time with this care.
Although, the pillowcase I use I just put it in the washer and dryer.Don't over dry and never bleach.  It has the same natural structure as your hair, so care for it a little more gentle.You can also add a bit of conditioner into the rinse water for softness if you are hand washing.