AFAIK they only need your signature on file once, period, when you first start Gold. I've used different credit cards over the several years and never had to sign again. You do need to put the additional cards in your profile online before booking or the Gold service is not guaranteed, but they've never needed to swipe a different credit card. I routinely use two different ones because for personal rentals I've been getting the $20 Amex insurance (applied automatically when I pay with Amex) whereas for business rentals I don't need that so I need to use a non-Amex card. Both are in my profile, both work no problem and neither one of these is the card I originally set up my Gold account with.