When your hairs tarts getting greasy (it will look like it’s wet and all shiny but not in a good way) you should do it. It depends on the amount of grease your hair produces. Some people wash it every day other every three days, it’s all about getting to know your own hair.
it depends on your hair really. For example, I H A V E to wash it everyday or it becomes extra greasy ive heard its an unhealthy practice but my hair gets really nasty so i have to wash it every day.