And it is no good idea: With it you make all other rules (for buying and selling) inoperative for a time, which additionally can produce a mess in your port (buy recommendation of a stock which is still in your port).
Better is to have rule(s) which do not lead to too frequent trades, in particular not to buy recommendations in falling markets.
Forget that with the buy recommendation of a stock already in your port. But it could be that a stock will not be sold although a sell rule was met before.
Anyway, I´ve done some tests in Excel with old trading results. There´s no advantage to “time-hedging” it seems. When you only buy “over time” you neglect the fact, that markets move in bursts of big up and down-swings. So you loose considerable profits if vou weren´t prepared to be all in, when you should have been all in. No advantage in the risk/return tradeoff. I´ll simply stick with holding a nice cash portion in my portfolio; makes the drawdowns smaller (at the expense of some profits).