Actually as long as you have another American Express Card the extended warranty coverage will still be in effect. I have had the fee free Costco Amex for many years and change my other Amex card for bonuses every year or two and have used the extended warranty benefit many times. I get the credit applied to my Costco AMEX, no matter which AMEX I used.

Beware of these offers in actually getting the points. I am still fighting with AMEX as I had a similar offered I applied for in March and have not gotten the bonus points and AMEX says they have no record. I just sent them a copy of my offer and we will see what they say now.