I used to fret about when finasteride would stop working for me. But, the way I see it, technology will continue to improve. Propecia/Proscar is one of the biggest money-makers worldwide, so there is a definate incentive for the pharmaceutical industry to pursue research in this area. So, I guess wait and hope is the real answer to this question.
I guess hair cloning represents the biggest hope of all male pattern baldness affllicted persons. But, I think that one is a long shot. Aside from being a political hot potatoe, the technology at the clinical level in humans is probably at least a decade away, even my the most hopeful observers. But, when and if it does come, it will render all of this worry and effort meaningless. But, then again, these are all big "IFs".