I've had a pair and a half go on me at this point.
In the first instance, my right joycon's analog stick would drift, and often fail to return to a zero point. I was able to consistently reproduce this issue, and posted the controller to Nintendo to investigate. No issue found according to them. I sent them video evidence of the issue occurring, and they gave me a refurbished replacement, apparently OK'd by QA. The first time I plugged it into my switch, the connection was loose, and rocked quite a bit. Due to this, the joycon wouldn't actually pair properly to the switch, so I ended up just buying a new pair out of frustration. I had tried to clean the analog sticks upon first encountering the issue, as advised by Nintendo and other people with the issue, but it didn't help me.
The second instance was for my little brother's switch. He had the drifting issue as well on the right joycon. So I bought a pair of joycons and kept the other half for myself. A week later his left joycon started the rocking and failing to pair issue I encountered with my replacement joycon.
Each of these things has happened about 9 months into owning the devices.