Sorry to be "lurking," but I was googling 'Uncurly' to see how a link displayed, saw your comment, and couldn't resist putting in my two cents. First of all, I'm glad you liked your results. Nothing makes me happier than seeing people get the kind of benefits I get from a keratin treatment without having to spend several hundred dollars. Once I tried keratin on my crazy hair, there was no going back, but $400 every few months was not happening.
Second, you mentioned that during the curing period your hair felt greasy and that ultimately you washed it out a little ahead of schedule because of that. Been there, done that. Two thoughts for the future: while the curing period can feel a little greasy, sometimes it's more so than it needs to be because of too much product being applied (doesn't require as much as you might think,but all hairs need some) and not enough flat-ironing during the application process. We always say iron until you notice a visibly significant reduction in the steam coming off, at which point there's usually a palpable change in hand-feel. The hair becomes less 'waxy' to the touch. While we emphasize this in the instructions, there's no substitute for experience, which you now have.
Second, as for longevity, washing out early can reduce it,but since keratin is TOTALLY individualized in terms of how it takes to each person's hair, there's no precise tradeoff. But I get that sometimes you've got to do what you've got to do! Again, thanks for your kind words about Uncurly. They made my day! Shelley Parker, Uncurly.com