Little known fact, "Limited Edition" can be limited by several things, in actual fact, the standard edition of the game is also limited, limited to a 4-week production before release, with more copies being made up at a later date to keep the market flooded with the product.
FM3 Limited Edition is probably limited by a shorter run of production, probably only a week, but in a week, several thousand can be made up. If it was limited by numbers, T10 would state that and probably number the individual copies. (Again, this is usually, as it's probably not limited by a set number, they won't be numbered).
I always pre-order the Limited Edition of games I want on release day, not because of the extra goodies (although they make it worth the extra cost), but because you are more likely to get it on release day. If that sounds strange, or unbelieveable, I'll explain it to you. Lots and lots of people pre-order the standard edition, lots of people walk into the shop come release day and pick one up without pre-ordering, even though game shops shouldn't sell pre-ordered copies, they usually do. Leaving people hung out to dry come release day. Pre-order an LE and there is less demand for them, so there are usually plenty left over after all the pre-orders have been fulfilled, meaning you can still get your beloved game on release day, if you are willing to pay extra.
How do I know all this I hear you ask? I work in the business of game distribution. (Well, home entertainment distribution, DVD's etc).