I agree. I might pack a good magnesium bar (Firesteel dot com has good ones) to prepare for the following unlikely scenario: I managed to get all my tinder completely soaked while it's about 30 degrees F. In that scenario, Mg shavings will still ignite from my ferro rod in the wet and cold. Also, there's a decent chance of the Mg transferring heat and igniting the wet cotton I was carrying, and so on.

Why would I not start fire with Mg on a regular basis? It's because successfully using Mg requires me to have a heightened level of focus and energy.

By the way, my Mini Bic will likely be working in the scenario described above. So, I'd try that first.