Guessing its a case by case thing. I received a code the other day hours before my order shipped and I even debated canceling. Sadly, I wanted the game and by then the $10 credit bonus was over so seemed pointless.
I'm in the same boat as you though. Pre-ordered a good handful of games with 25OFF and not sure if I'll have any codes coming but I'll drop them a line tomorrow and see what the deal is. What games did you pre-order by chance so maybe we can connect up some dots on why they sent you only 3?
I preordered the following games:
Alan Wake Limited edition
Prince of Persia
Red Dead Redemption
Good luck with your email. Hopefully you will get some codes..