thinking about buying finpecia from inhouse pharmacy...my main concern is the legitimacy of the product , and secondly...what about long time use, im 22 now if i take finpecia for the next 40 years is it going to lose its effect over time, is the dht going to find some way to override the finpecia and still cause baldness? i guess im scared to start something and have it all be a waste after i hit 10 years of use....does it keep working?