I think 2-3 times a week is recommended. I workout nearly every day and my scalp starts to itch if I don't shower, so I need to wash my hair once a day at minimum.
It depends on the person, I used to wash my hair everyday but I think it was really bad, I started about a month ago, washing once every 2 days and inbetween just rinsing with water to remove product/bedhead.
If you keep stripping your scalp to a barren state, the scalp will produce more oil etc.
