I meant 7.2 years. I was writing from memory.
Even though I'm using the term "cycle", it does not have the specific characteristics as a Hurst cycles with harmonics,nesting of lows, translations, inversions, or straddles. It might be better for me to use the term "oscillation", because the output of band-pass filters are sinusoidal. Hurst's book does briefly touch on spectral analysis, which is my approach; however, since the math is beyond the abilities of many readers, Hurst tried to distill a simple model that more people could understand and apply.
When I searched for longer cycles, there is something in the 19 year duration that might be topping. I do not have enough cycles to get a high confidence reading. I see only a peak, trough, and slowing momentum; which is enough to be on alert for a bear market lasting longer than either 2000 or 2008.
I do believe the FED activity is showing up, but in the amplitude of the 3.3 year cycle. The FED could not stop the 7.2 yr cycle, and businesses are more aligned with a 3.3 year cycle than a longer 7.2 year cycle. That's why I believe the 3.3 year cycle has been the dominant cycle of this last 18 months of the bull market.
