I've had a prepaid card that doesn't expire for a few years now, and keep it in my wallet in case there's no cellphone coverage or my cell doesn't work (no juice, broken, etc.).

The pre-paid cards work pretty much everywhere. They are so cheap, we cancelled our long distance service at home and use them on our home phones. We've also used them at many pay phones (no coins), and in Russia and Africa, no problem.

When you use it all the time, the card is optional, the numbers are in our head...

I haven't used pay phones in years. One of the issues I ran into was poorly maintained equipment, would often be able to make a call but the other end couldn't hear me due to crap in the mic end of the handset but still would get charged for the attempted calls anyway.
Then they started disabling the keypad after the call was complete. So you would dial your calling card company and when it was time to plug in the card number it wouldn't work.