I'm still new and confused by the whole credit card churnning process.

I have 1 CC, a delta Amex that came with 70K miles. I'm about to sign up for a 50K chase united card and maybe a usair card if I find a good deal.

At the end of year one, what do you do? Close the account? Pay the yearly fee? Downgrade to a free version of the card that is not airline branded?

How do I then become elgible to do this again in a year or so?