I can only speak for the GameStore where I worked at the time, but it worked out something like this:
7-8 months before release: Ninty says "We will have 120 units for your store at launch! OK to start preorders for that many!"
1-2 months before: Ninty says "Uhm, more like 60 units"
1 month before: Ninty says "OK OK, 30 but no less. We swear"
Less than a week before: Shipment from Ninty is verified as being en route. TWELVE units.
Had to call preorders in the order they were taken based on how many units actually got delievered: "Pick it up by close tonight or we will have to call the next person in line tomorrow and we'll call you on the next shipment". I don't think anyone failed to show on time
It took us until March just to deal with preorders...and hundreds of people calling/coming in every day asking for the things (we actually kept a tally on paper one day. we gave up at two hundred calls in THREE HOURS) >_< We would have loved to have been able to sell to them, too, but ya can't sell what you don't have. Mercifully, the ravages of time have erased what little I experienced in the way of SC's because of this.
Word has it that the big N decided to favor the big box stores, and looking around IRL/reading seems to have borne that out.