I assume you are talking about PCT. Personallly, I prefer Clomid now days, but Nolvadex works too. 3-4 wks is a good length for a PCT. I might incrase the dose of nolva for the first week...a loading phase. 40mg for wk 1 of PCT. Then 20mg for 2-3 more wks. Arom at 12.5mg is good too, in addition to the SERM