I did some Googling and there doesn't seem to be an epidemic of 3DS game carts failing, I can find a few isolated reports but that feels as expected to me.

It also sounds like you can extend the lifespan my making sure to boot up your cartridge in a 3DS every so often, because Nintendo gave them an error correction routine: https://gbatemp.net/threads/nintendo-switch-3ds-cartridge-li...