Hair dilemma

My friend Megan and I always consult each other about our hair. We have a similar hair type and tend to cut it/grow it out at the same time. Right now, we want the longest hair possible. With thin hair, this can be difficult, as it can only hold so much weight. I feel like I may be maxed out at the length I'm at right now, but I'm still looking for ways to keep growing.

I have certainly been stressed out, and my diet has been lacking. My hairdresser/life guru told me to up my protein intake and try not to use the flat iron. Some suggest biotin or prenatal vitamins. My friend Shannon is a firm believer that less washing/more dry shampooing does the trick. She's such a believer she bought me a shark shower cap for Christmas so I'd stop washing.

Does anyone agree with these philosophies? Any other suggestions or wives tales? I really want to add a few more inches of length!