I have recently been converted to the joy of filling in credit card details (and address and phone number and...) with LastPass' form fill function. I previously had my CC details memorized for similar reasons, but I didn't realize just how much time I was wasting typing this stuff in over and over until it was magically done for me. And since security is what LastPass does, I have no problem with having their extension save my CC info in a secure manner.

I am an avid LastPass user and I already have my CC details in LastPass. But, until now I didn't realize you can add them to the Form Fill details! Thank you tempestn!