DCA - intervals

[Untamed]

Given my lack of significant disposable income, my investment strategy has pretty much always been, dollar cost averaging. I have generally invested at weekly or fortnightly intervals, in line with pay days etc.

Is there an optimal interval for DCA? (I have a Sharesies $3 monthly plan, so transaction fees cost is minimal).

[Ennui]

Jeremy Siegel, Stocks for the long run (recommend reading, I borrowed from library) from memory, mentions investing near the start of the week (peak pessimism). There may have been something in there about monthly timing. But the book is quite old now, has aged well, but may not accurately reflect todays environment with index funds etc).