You only need to wash your hair once or twice per week which is good enough to keep your hair clean and healthy.
Washing your hair more than twice per week or washing your hair everyday can dry out your hair and remove essential oils from your hair too that are needed to keep your hair moisturized and healthy.
If you need to wash your hair more than twice per week then use a moisturizing shampoo to keep your hair moisturized.
But if possible avoid washing your hair more than twice per week to avoid stripping your hair of the essential oils that are in your hair and to prevent drying your hair out.