And it’s fine! 
I wouldn’t believe me either if I saw this post 6 months ago. And no I’m not selling anything either. 
All my life I’ve had to wash my hair daily. It was greasy by the end of every day and my scalp would drive me insane with itchiness. Around 4ish months ago I noticed it wasn’t as greasy every day and I started leaving it an extra day and then an extra day until I was managing a week without washing and no itchiness. None at all. I last washed it on the 12th of May and today it started feeling greasy the way it used to on day two when I was washing daily. I am in shock. I never ever thought I could get a fortnight out of my hair. I used to think my aunt was lying when she said she only washed hers once a week. The only change I can think of causing it is achange of shampoo. I now use Cien tea tree shampoo from Lidl. It’s very cheap and now a bottle is lasting forever
however I can’t remember when I started using it and if it coincides with new hair behaviour. I’m 31. Could this be an age/hormonal thing? My diet hasn’t changed.