I've been sulphate free for near two months now. I use Naked shampoos but am transitioning to Aveda DR Poo.
From the research i carried out then, sulphates erode the hair shaft over time.
So though damage may not be noticed immiedately, it is more likely to occur overtime.
I also noticed that Naked poos left my hair feeling hard, then i added a bit of oil to it and it felt better. Aveda DR poo has been great on my hair so i hope to use it exclusively in the future.
At the mo, I dont shampoo much. I do more co washes + DC's on dry hair. it not only shaves hours off my hair care routine, it makes my hair feel great!