I don't know if this is accurate, but i am of the belief that every hardinquiry lowers your score b/t 2-7 points. The negative point drop reverts back positive after 90 days to your credit score (I don't know if this is 90 days after cancelling the card, or 90 days after the inquiry even if you keep the card).

However, the inquiry still shows up as having a credit card for 2 years, before that credit card disappears from your credit report after it is cancelled. I think. I can't remember.

Even still, i'm sure if you apply too many times, say 12x every 6 months, that that can't be good for your credit.

Where should you draw the line?