Using it every other day would be the most I would suggest, as long as your scalp likes it. HOWEVER, I would add in that I STRONGLY believe that you should not just rely on ONE antifungal and should occasionally vary your antifungals to avoid the flora on your scalp from becoming resistant to them.
I suggest using Nizoral predominantly as it has other beneficial anti-male pattern baldness properties over and above the antifungal qualities, but once a week I suggest mixing in a different antifungal, such as T/Gel and Head and Shoulders.