male pattern baldness is a progressive condition, meaning no matter what you do, your follices will produce more 5ar2 to make DHT and will have more androgen receptors to get affected by this. This is purely genetics and age determined, and is different for every person. You can get more sensitive every year, or stay at the same sensitivity for a while. If you look at the placebo group on my avator, you will see that they lose hair faster with time because their hairs are getting more sensitive.
Finasteride does not stop this process. It just reduces the production of DHT. If your follicles can handle the reduced amount, they will live. If they continue to get sensitive and eventually can't handle even that amount, you will find that finasteride is "no longer working for you". It does not stop hairloss in the very beginning for 17% of men, and many of them come here or just quit. When they quit, they loose the hair it had been protecting that whole time. A link to my avator is on myspace. You can find it or google image search: propecia year.
That 17% will grow over time as people age. That is why I am using more than just propecia in my regimen.
Also, men who bald before age 23 probably have aggressive hair loss and are much more likely to be in that 17%. Applunk 1 started dutasteride 0.5 mg per day 6 months after his hair started thinning. He has been battling it for two years with that and spironolactone and SODs and is still loosing the battle over his entire head. Bryan is probably 40 and regrew his hair just using Dr Proctors products without propecia, since his male pattern baldness is less aggressive.
Propecia is barely maintaining my hair. Since I did not get the average 90 hairs, I know it will fail me soon if I don't start fighting with other stuff now.
The only advantage young men have over older men is we are much less likely to get side effects because we have more testosterone.