Oops. Now that was embarrassing. I started a new topic and left out my findings that I wanted you to read.....here it is:
If you go to Dr. Peter Proctor's site Dr. Proctor, you might find reference to some material about "resistance" building up after using minoxidil three or four years. He has heard from other doctors that perhaps 30% of patients no longer respond well to Rogaine after using it for long periods of time.
Other doctors report that Propecia (finasteride) is also subject to resistance. The human body builds up a tolerance for this drug after a time by producing more DHT. If I find specific references to these findings, I'll post them.