>Whether market timing is ever a viable investment strategy is controversial. Some may consider market timing to be a form of gambling based on pure chance, because they do not believe in undervalued or overvalued markets. The efficient-market hypothesis claims that financial prices always exhibit random walk behavior and thus cannot be predicted with consistency.

https://en.wikipedia.org/wiki/Market_timing

What you are planning seems like a good idea but buying bottoms can be really hard. Lot of info in that wiki article. I like that you are thinking about it though! That already puts you ahead of a lot of the game.