My daily driver car experienced an inertia switch failure the other day. I was surprised at the condition of the failed inertia switch when I removed it -- it had clearly experienced overheating and was visibly deformed and melted in places. I presume that over time the electrical contacts within the unit degraded, resulting in some resistance though the unit and associated I^2 * R heating. Because it's in a location that is easy to overlook, you might consider examining yours the next time you're doing periodic maintenance to verify that yours is not showing any signs of heating. Mine had 160,000 miles on it. Knut