When I initially started finasteride I had almost instant results, hair had thickened up and regrown within 3 months. As spring approached I began to shed and this lasted all the way through summer (7 months). After this things stabilized and I regrew more hair (a lot more than the first time around) within the space of a month and a half, this was November last year.
Since November I have been shedding quite a lot of hair but it seems to be slowing a little now I have added nizoral to my regimen. I think the bottom line is that these drugs can be quite unpredictable but I have genuine confidence that shedding hair is a positive sign. I believe that as long as you ride it out you will eventually experience more thickening and regrowth.