Yup, but you do not know whether the strain will be released in a big quake or many smaller quakes. You could be at a state where a lot of strain has built up a

Yup, but you do not know whether the strain will be released in a big quake or many smaller quakes. You could be at a state where a lot of strain has built up and a megaquake could seem immanent but then a smaller quake relieves some of the stress and "resets the clock". And then are you still "overdue" or not? The way things work over very long periods of time is that some faults exhibit some degree of periodicity in terms of large quakes. But simplifying that periodicity into the concept of being "overdue" for a big quake is intellectually irresponsible.