Who hasn't found a juice or coffee stain on the sofa? Cushion covers can be machine-washed, but the frequency depends on the fabric type. Cleaning them every 2 or 3 months is advisable, with some exceptions. For example, Christmas and seasonal cushion covers should always be washed before being put away in the cupboard.
Always check the label to be safe because some materials require special attention. Suppose your zippered sofa cushion covers have foliage prints or other decorative patterns. In that case, you should wash them at a low temperature and only with mild detergents.
To preserve the colors and details of the prints, you should wash them gently or by hand. Also, always dry the cushion covers well, preferably in the open air, to prevent them from developing unpleasant odors.
Is it really that important to wash cushion covers? Absolutely! One research study found that unwashed covers can harbor more bacteria than the toilet seat (more than 17 times)!