Does DCA frequency matter more or time in the market?

I don't think DCA frequency necessarily correlated with investment returns. Rather, the more often you DCA, the more closely your portfolio mimics the market/index performance.

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And since the market generally goes up over time, if you invest in broad index ETFs, your portfolio should go up over time, and time in the market (ie more frequent DCA) leads to greater returns.

A general rule is that the more volatile a portfolio, the more frequent DCA will be better.