I've spent a huge amount of my life typing on a keyboard, and I've never had a switch fail. Is this a legitimate concern?

It’s more common on mechanical keyboards than membrane. I have had mechanical switches start double clicking. Never had a membrane keyboard fail.

It’s obviously a YMMV kind of thing, but I’ve had mechanical keyboards in the past with failing switches (one Cherry MX switch, and three Matias Quiet Click switches on three different keyboards!).

Matias Quiet Click are very prone to this. I've had 3 fail on one board and 2 on another.

I don’t think it’s going to die for another decade, but we’ll see.

If the push comes to shove, I think I can solder a single switch from a major manufacturer. I’m not the one to shy away from a soldering iron at the end of the day.