One thing to be aware of is that cancelling your Costco AMEX card will be a slight hit to your credit score. My Costco AMEX card is my second oldest card so the age of my credit history would go down, possibly reducing my credit score. Also, getting a replacement AMEX card would drop it. I ran it on a simulator and adding a new card dropped my score by 2 points. Unfortunately, I got a message that dropping my oldest card gave unusual results and to try again later.