Re-reading my old thread and wanted to respond to what you wrote here. "You wrote never perform keratin over and over on the same hair once you've reached your desired curl pattern." Well, after 2-3 months of keratin, the hair pattern usually reverts back to its natural texture, or at least 80% of its natural curl texture, so it's no longer your "desired curl pattern" which is why one re-applies the keratin. What the salon's don't tell you is despite the fact that your hair reverts to its old curl over time, the product still accumulates on the strands so with each keratin process you end up with straighter and straighter hair.
In my experience, my best curl pattern was reached after treatment #2. After a couple of months, my hair got curly/frixxy again and no subsequent keratin treatment gave me results like that again. It just got duller and limper.