> NFC is fast and reliable

I know you're speaking of NFC chips in cards, but you might know — Does the phone version (Apple Pay/Android Pay/Samsung Pay) still work when my phone's battery is dead?

It won't - one reason why I think NFC-enabled cards will be around for a long time even people only carry one as a backup for their phone.

Though theoretically your phone could have a RF-powered NFC chip in it that took over when the phone is off...