7-Eleven normally doesn't have 7.11oz Slurpee cups. So it's probably that each location only gets 1000 "special" cups. When they run out of cups, maybe they will let you fill a regular cup 2/3 the way. I doubt it though.

I would assume they start giving them away at 4-6AM. There are too many hoodlums that hang out at the Stony Point, NY 7-11. I used to be one of them (nothing better to do in a small town). The hoods would probably put too much of a dent in the cups to start giving them away at 12AM.

If you want one at Midnight, you could probably bring in a printout from the web. They will probably just give it to you to get you out of the store.

Speaking of free food... I just got back from PF Changs where the Lettuce Wraps were on the house for some unknown reason. Free lettuce wraps and Slurpee.... This is turning out to be a great week.