Dangerous. OTOH if someone did the "buy the day after the dip" and "sell the day after the next peak" then they'd bought Netflix stock on Dec 27, 2018 at 250.11 and sold at Jan 09, 2019 at 317.71 -- it's 25% in two weeks...
How would someone actually do that? The only way to identify the dips and peaks is N days afterwards, where larger N increase the confidence of that it really was the max/min.