If you wore something under your sweater, for example, that will extend the life of your sweater by reducing the number of times it needs to be washed, she says. Material-wise, things like cotton, cashmere, and silk should be washed after two to three wears, while more durable materials like wool or hardy synthetic blends can be worn up to five times. In short, you definitely don’t need to wash your sweaters every time you wear them, and if you want to spread out the time between washes, your best bet is to wear an undershirt.
