When I started Finasteride my already ongoing shed decreased by half. After close to a year my shed completely stopped (IE maybe lost 1 - 5 hairs a day). Then around the 17th/18th month I started shedding 25 - 50+ hairs (keep in mind these are hairs I noticed and does not take into account hairs lost throughout the entire day).
My point being, if you never get a shed consider yourself lucky! Some guys dont whereas some guys do (whether it is right off the bat, mid way into it, or several years down the road). Why? Could be synchronization of hair cycles, could be increased sensitivity to remaining androgens, could be anything really as there seems to be a new question produced with each answer to hairloss we find.... So who knows!
Dont count yourself out of getting a shed just yet bud... Took me 18 months but I finally got paid a visit by the Shed Gods... I hope ya dont though!