Continuous events or events that occur regularly should be avoided. Instead, their effects should be computed (based on the elapsed CPU time) when they become visible. The archetypal example of this is a cycle counter: instead of invoking the model to update the value on every cycle, the model should compute the value on demand whenever the counter is read. If the value is read every N cycles, this replaces N increments with one subtraction. If the value is never read, no computation is performed at all.
This principle is valid even if the computation takes as much or more time than the sum of the individual updates: if the value is never needed, it will never be computed, and even if it is, it is usually more effective to optimize the model by reducing the number of invocations than by reducing the time spent in each invocation.