You might be interested in the work of Palden Jenkins, who has a huge web site: http://www.palden.co.uk/
Among other things, he's a practicing astrologer, and he wrote extensively on these major outer planet cycles, Neptune/Pluto AND others, and you could certainly do your own research on these and update where he left off, and, as Rad pointed out, relate them to Evolutionary Gates.
The section called "Historical Ephemeris from 600BC to 2200 AD" will give you hours... days.. of "entertainment" and information: http://www.isleofavalon.co.uk/ephem.html
Here's his brief description: "Astrological tables and historical timelines demonstrating the relationship
between world historical trends/events and planetary movements for the use of historians and astrologers
researched and compiled by Palden Jenkins"
And this: "Contrary to current historical ideology there indeed are identifiable cycles of change in history.There is a surprisingly clear relationship between slower planetary movements and historical events and trends.The deeper causative thoughts and beliefs of humanity often take time to manifest as events, yet their beginning-points are identifiable astrologically. Human free-will does affect the manner by which historical events and trends manifest and a study of astro-history shows the many ways this works.The events and changes of today, around Year 2000, actually have their roots in the 1890s.These are some of the many conclusions you're likely to come to after studying these tables."
I hope you enjoy his site as much as I have!