The leap day system handles the mean, the leap seconds handle the variance around the mean. The need for leap seconds is not predictable—they zero out accumulated error.
My attitude has always been that code review is best thought of as the gate where code goes from being owned by the author to being owned by the team or project. The code I'm reviewing is not your code, it is code that is about to become our code.
Maintainability is a major factor in that, of course.