The reason that our conceptual models look incredibly smooth and predictable is the fact that they are a composite of all previous observations, which tends to have a smoothing effect on the data.
When looking at the peaks and troughs of current cycles, however, the period will not be consistent, and will usually be expressed as an average. There will be at least some deviation from the average timing most of the time. Given that, it makes sense to think of cycle peak and trough timing in terms of a “window” of time, rather than a specific date.
In practice, most peaks and troughs tend to fall within 15% to 20% of theoretical timing. Once a cycle has been modeled and an adjustment made for bullish or bearish translations (left-hand/right-hand), a 15-20 percent window should be established as the window of time to be looking for the actual peak or trough. See below for a graphical representation.