Their history is spotty for identifying the absolute long term top before significant declines in the industrials, but they often warn of impending weakness on an intermediate term basis. For example $Indu completed a monthly TD Combo sell signal in May 2007. It completed a TD Combo sell signal two months ago.
It's history in the SPX is spotless but no signals pre-date the 1990's.
One should use shorter term signals for trade entry decisions. The daily and weekly charts are in substantial alignment with the monthly.

