I love the stuff. I've posted on this already recently, but it feels like a genuinely good shampoo with at least one proven ingredient (keto) and a bunch of unprovens.
I have used it five days a week since September 2009, though I do not use Revita strictly as instructed on the label, which says apply for 1-2 minutes, rinse, and apply again for 3-5 mins. I've always heard "rinse and repeat" instructions like that were BS. So instead, since I had some Nizoral left over when I first bought my Revita, I use nizoral as the pre-wash to it three days a week. The other two days I use just a regular shampoo as a pre-wash. My scalp has handled it all fine.
I believe someone recently mentioned that it isn't the keto that burns you out in Nizoral overuse, but the other ingredients in the shampoo. Take it for what it's worth, but like I said, I've been fine.