Worth noting that, via Nintendo:
Repairs are completely free
Shipping is completely free
They repair up to 4 JoyCons at a time
There is no limit to repairs
I'm a big proponent of DIY culture, but there is literally no reason (for US customers, at least) to take advantage of this free corporate offer.
I sent in 4 totally fucked joycons and they were returned 100% perfect within 3 days. They even fixed my connectivity issues with one JoyCon (or replaced it), even though the guarantee is for sticks alone.
Don't waste the free money Nintendo is giving you, folks. IMO, everyone should take advantage of this very convenient service.