I have the 2%... it's not going to kill you if you add a 3rd day. In fact, if you're like me, you won't suffer any adverse effects. I started off using it twice a week, but it makes my scalp feel SO MUCH BETTER that I started using it more frequently and it doesn't dry my head out. I think all that oil counteracts it, but for the day it makes my head feel great.
No, I don't use it every day. I don't even use it every other day on a consistent basis, but I've used small amounts to wash my hair at the end of the day without letting it sit for the 2-5 minutes. I'd say I use nizoral anywhere from 3-5 times a week.
FWIW, I am someone who is reversing my male pattern baldness through the big three. So it's not like I'm just some dude who rubs nizoral into my head a bunch and isn't seeing any results.