The late technician, George Lindsay described an 8-year interval as part of his 22-year Overlay (An Aid to Timing, SeattleTA Press, 2012). He wrote that the high (or "moment of truth") at the end of the interval is often followed by a harsh 2-3 month decline followed by an approximate 5-month rally in equities.
With the Dec 2014 high marking 8years, 5months since the low in July 2006 (and fitting the template for the 22year Overlay) a 2-3 month decline would match expectations for a 14m low in March.
A 5-month rally from March comes very close to the seasonal expectation for a high in early Sept in pre-election years (chart: 1943-2011).
To get your copy of the January Lindsay Report from SeattleTA, please click here.