Well, yes. The breaking strain on any single fault is an individual property which changes over time: when one asperity breaks the next one takes over and it will probably be different. Also, it is probable that the local loading rate is variable over time even if the overall plate velocity is constant.

The saucer analogy is a very simple case; the reality in the earth's crust is highly complex.

Responding to Petra, the problem is that while there may exist precursors which have been observed before some earthquakes, there is no law which says that consistent earthquake precursors MUST exist (and by extension, if you look hard enough you will eventually find them). It may be the case that what we think of as precursors are better defined as some of the properties of crust under near-critical strain loading. Because such a loading state is generally followed by an earthquake there is a correlation between precursor and subsequent earthquake. But, for instance, if the loading rate slows down, the critical state could be preserved for some time and you would observe precursors but no earthquake.