Depends upon the hair, but, no, it actually doesn't always revert back and "desired curl pattern" varies from person to person and hair texture to hair texture--my "desired" curl pattern may be looser or tighter than someone else's. There is a point of no curl return after BKTing with all hair types, and the finer your hair is, the sooner it reaches that point. If you have coarse "horse hair" you can do more repeated treatments before the curl finally reaches a no-return stage. The product does not accumulate permanently on the hair strands. It washes off progressively. Accumulation of the product on the hair strands is not what causes the straightening.
I've been doing this for almost 3 years. I know what I'm talking about. I haven't had to BKT my entire head for 2 years because the curl pattern is permanently relaxed after 2 applications; I've only been retouching my roots every 5-6 weeks for 2 years now.
When I retouch my roots, I overlap about 1/2 an inch into the previously BKT'd hair, so all hair gets two subsequent applications about 6 weeks apart. That's all it takes. My previously resistant 4a/3c curls are forever relaxed to about a 2b/2c. In fact, I wish I had a bit more curl in my hair these days. Results are not typical because my hair is SUPER fine, so not much of a keratin layer of its own.
It's so frustrating for me to read all of the misinformaton that's circulating around because I've done so much trial and error and have consistent, reproducible results now.
It does not repair hair.
It does not attach to the hair shaft permanently.
It is not always a temporary solution--can be permanent depending on the texture of the hair and the treatment brand used and how many consecutive times BKT is applied to the same hair over and over.
The key determinants in results and how permanent and how dramatic your curl relaxation are:
Which brand you use.
Hair texture (fine vs. coarse and where it falls between the two extremes)
How often and how frequently you BKT the same hair back-to-back.
It can be used back to back to achieve looser and looser curl patterns.
QOD does not damage the hair and cause breakage in the way that repeated use of heat, hair color or relaxers do. My hair stopped shedding in May, and what I discovered is that my hormones were weird from about Jan. to May. My hair shedding slowed down from about April to May, and it is back to normal now, and my hair is back to normal overall. The shedding had nothing to do with BKT.
The only breakage I have suffered in the nearly 3 years that I have been BKTing regularly is from the heavy highlighting I had done in 2009 and early 2010, which I haven't had since. That's the only hair that has broken off...you can see how straggly my lightened ends are, while the dark new growth is thick and healthy.
Trust me...I have the finest, most fragile hair I've ever seen on a healthy adult human, and my hair is almost down to my waist after 3 years of BKTing. Believe what you want, but they'll have to pry my QOD Gold from my cold, dead hands.
I'm 46 years old...I've been fighting my hair since I was about 10--when I cut it all off and started relaxing. I didn't make peace with my hair until I was 43 years old--when I started BKTing. My hair is almost my dream hair now. It's awesome and has changed my life DRAMATICALLY. If I'd had hair this carefree as a teen and young adult, I'd be a completely different person right now. Yes, it's impacted my life that dramatically.