The average steady-state serum dutasteride concentration is 40 ng/mL following 0.5 mg/day for 1 year.
Following daily dosing, dutasteride serum concentrations achieve 65% of steady-state concentration after 1 month and approximately 90% after 3 months.

So to me that means that you'd need to take it for a year before you'd have a constant level of Dutasteride in your blood?...
So what?, to be sure (or as sure as you currently can be) of effectively reducing the likelihood of developing DHT related side effects, you'd need to take it for a year prior to starting your course?...