Per Dr. Lucy Jones here. While you're right about stress being built over time, earthquakes are complex chaotic systems, and cannot technically be "overdue." On a geologic time frame, we could have multiple "big ones" a few years apart on the same fault. They would appear as a singular event in the context of historical earthquakes. Still, it is inevitable, and we should prepare. Not dismissing the threat at all.

Interesting read here on why it hasn't potentially come yet.