only tangential, but I've wanted to carry my Yubikey on my keyring, but have always been nervous about making it unreadable by sullying the contacts. Should I be concerned about this? Where do you all carry them?
That's how I've been carrying mine for the last four years and it's fine. I think you're more likely to lose it than to damage it. I have a second one that's identical (registered to the same services) that I keep in a safe place.
I came across https://www.thingiverse.com/thing:2588513 in some Reddit thread about this, got it printed on my public library's 3d printer, and it's been pretty nice. (Had to etch some grooves in the sides of the Yubikey so there's something to grab it to pull it out of the sheath, but that wasn't a big deal)