My understanding is that any QEC code is able to detect and correct a certain number of physical errors on its qubits and this is the code distance $d$. If we have more than $d$ errors in a given round of error correction, we can no longer guarantee that we have decoded to the right state i.e. we may have a logical error.
To get a notion of time, I will look at the number of gates in my circuit. Doesn't this mean that if we wait sufficiently long (i.e. have a sufficiently deep circuit), we will have at least one round where we have more than $d$ errors with arbitrarily high probability?
Does this mean that all QEC codes must eventually fail?