As with many things since the birth of the internet, there are many "professionals" that will try to coach you on all sorts of things. Fortunately, I am here (presenting factual items) to clear some of those conflicting ideas given to you by, most likely, your best friend, your mom, and/or let's not forget the aunt.
From a simple perspective, that seems logical right? I mean, I wouldn't blame someone for misguiding me in this, because it makes sense! However, the hair is not that simple. That is, as your hair grows, the stabilizing bonds (primarily disulfide bonds, as depicted to the right) that make up the hair eventually degrade (they bind protein chains together, in this case chains of keratin), causing a loss of structural rigidity (chemwiki.ucdavis.edu). With this loss, the hair ends begin to fray, or split (because these are the oldest parts of your hair). If left uncut, the split ends will no longer just be at the ends, and will cause hair loss (imagine once you break a plastic seal on something like a book, how easily it splits up once it is punctured). Thus, regular quarter-inch trims every six-eight weeks will help prevent this. On a somewhat related note, keratin conditioners alone will NOT repair this hair, as again, it is the stabilizing bonds that are lost, not the keratin; the hair is actually still abundant with keratin.
While there are somethings you can do to stop or stunt hair growth, more than likely if you're actively trying to grow your hair and it won't move past a certain point, you are at your limit. In fact, our hair is genetically determined to grow to a certain length (hairscientists.org)
If your scalp or hair smells, it's trying to tell you something. The oils which are secreted from our scalp, as well as the products we put into our hair, produces a great place to live for many fungi and bacteria! These guys usually like warm, moist areas. Not to mention, if our scalp is covered in product buildup, it makes it much more difficult for our hair products to be absorbed, which is counter to the reason why we haven't washed our hair in the first place, isn't it? What is the take away message? While obviously shampoo is "damaging" to hair by its very nature as a detergent (this is necessary to kill bacteria/fungi), washing your hair with shampoo is a necessity to kill these microorganisms! "Cowashing" alone just doesn't get the job done.
Ophardt, C. (n.d.). Permanent Hair Wave - Chemwiki. Retrieved August 26, 2015, from http://chemwiki.ucdavis.edu/Biological_Chemistry/Proteins/Case_Studies/Permanent_Hair_Wave
Stevens, C. (n.d.). Growth Cycle - The Trichological Society. Retrieved from http://www.hairscientists.org/human-hair/growth-cycle