I have thick, wiry hair that is somewhat highlighted but mostly gray and I have color done every three weeks and highlights (very few) every 3-4 months.
I don't think the Keratin Treatment stayed in my hair very long either -- and I do NOT wash it every day (I wash every 3 days).
I was very careful about product use so as not to ruin the effect. I just think my hair is resistant to a lot of things (color included). HOWEVER, I will likely try this again as I understand for those of us with resistant hair, the second time around is even better. If I see nothing outstanding on treatment #2 - I can at least say I gave it a chance.
I had it down on 4th of July weekend -- and noticed that it was losing that 'frizz free' look around week 5 or 6. I still think it is somewhat easier to blow it out now -- as opposed to before the treatment.