...you can see that even after 5 years, propecia users still had significantly more hair than they had before starting propecia. The study has not been updated to include the 10 year results yet. But the graph trend implies that there would be minimal further loss over years 5-10. The rate of hairloss appears to slow down with increasing efficacy for each year the medication is taken.
Anecdotal reports in this forum suggest propecia maintains its effectiveness even after 9 or 10 years. So, to answer your question:
So lets say I start taking it now, is it possible I wont bald?