in regards to irreversible inhibitor, I am guessing that is just a scientific term that doesn't really mean what it sounds like.
"3. Enzymes Are Rebuilt Within Two Weeks (The Great Majority of Times). Research shows that it takes your body two weeks to rebuild the missing enzymes generally. This is based on the observation that "multiple daily doses for 1�2 weeks led to a similar 65�80% suppression of serum DHT, suggesting that tolerance did not develop to a chronic finasteride regimen in men. It has been reported that DHT concentrations recover within 2-weeks following the cessation of finasteride treatment in men , a finding that would be consistent with the slow turnover for the human Type I and Type II enzyme complexes." [3] Again, this is similar to the recovery time from Aromasin mentioned above."
http://www.peaktestosterone.com/Propecia_Irreversible_Inhibitor.aspx
I am not a scientist nor medical student but its my interpretation that a drug that is irreversible (by the non-medicinal definition) requires gene therapy that acts at the DNA level which just is not a thing right now, so I don't really buy it. Your body gets the cues from DNA at the end of the day. Are you telling me finasteride tells your body to indefinitely shut off DHT production? I don't find that plausible.