I am 40 and the hair is starting (quite early stage) to go up on top, although I am not really receding.

I have thought about Propecia, however, I'm not sure I want to take it forever. What would happen if I used it for 10 years and then stopped? I believe I would lose any growth that had occurred due to Propecia, but would I then loose all the hair that would naturally have fallen out during those 10 years?

I'm not trying to stop the aging process forever, but I wouldn't mind delaying it 10 years. I'm just concerned once I stop using propecia balding would progress at a very rapid rate (play catch up).