The more sensitive the hair follicle in question is to androgens the more DHT must be reduced to halt/slow the process. finasteride caps out at 85% of the DHT produced from the type II 5ar (overall DHT reduction of about 60% - 65%).
Also remember that while DHT is the main androgen thought responsible in male pattern baldness, testosterone is also an androgen present in the hair follicles. finasteride does not inhibit any testosterone and might actually increase such levels via stopping the conversion to DHT.
You're better off with higher testosterone levels and lower DHT levels but if your hair is sensitive enough (and the frontal areas tend to be the most sensitive) the balding process will continue.