You are right about the seven day cycle. This cycle was even more pronounced after the hardfork. The cycle creates a predictable drop in the price of HIVE.

The odd thing about predictable events in financial markets is that they work until there's enough money in the market anticipating the predictable event ... and then the predictable event stops working.

If you want to play this part of the market, I would actually follow the power downs. The Financial Reports by arcange summarizes the power downs. I guess the smart way to play the powerdown phenomena would be to subscribe to HiveSQL and look at the total power downs.

BTW, the price of the alt-coins are far more indicative of sentiment. People playing the market in Hive-Engine pull their funds from Hive-Engine and the price of the alt-coins plummet with each ATH.