It has been my understanding that the Southwest/First USA Visa card limits you to earning 5 segments for transferring up to $5,000 for the lifetime of the card.
I have had great success negotiating with Diners Club when it came time for renewal. For two years in a row, I mention that the American Express card seems like a better deal....that makes them go bezerk! When I first signed up for DC, I received 20K points instantly. Year 2 was the same deal. Year 3 was 2K points per month for one year as long as I used the card at least once a month.