I had one brand new Kingston CF card fail on me a few years ago. I'd just received it, took a few test photos then found I couldn't read the files in the computer. I eventually rescued the images and then returned the card.
Now I tend to use Sandisk and have not had one die on me.
I think Dave's point about not pulling cards out and putting them back all the time was valid when talking about Compact Flash because you're pushing a connector onto pins, some of which can get bent. But when it comes to SD cards, they don't have pins, so it's less of an issue.
You could connect your camera to the computer each time to download images, but often the transfer speed from the camera is slower than from a proper card reader.
As for the Wifi question; if you have a camera with Wifi, then it might be worth testing out wifi transfer to a computer while shoot. I doubt a phone will have enough space or processing power to deal with RAWs and you'd probably drain your battery using it like that for a whole day wedding.
A few companies like Western Digital make wifi hard drives that could provide a better option. But actually looking at this model:
https://www.wdc.com/en-gb/products/portable-storage/my-passport-wireless.html
It might be a good option for a big day of shooting. Fill a card, take it out, put it straight into the SD slot on the hard drive, copy files over and carry on shooting.