When it comes to Newsletter success, consistency, and by that I mean daily, is everything. I started mine* about a year ago and while it's still considered a hidden in gem in comparison to those who raffle of Teslas as a growth-hack, three hours of daily work have gotten me quite a list of renowned subscribers. We're far away from the peak — the problem is that too many people think they're interesting.
Bonus: Don't use Substack — Own your shit from day one.
I think the appropriate frequency is (should be) derived from the subject matter.
Some subjects deserve daily coverage, but the vast majority do not.
Nearly all of the newsletters I subscribe to and actually read are weekly, with a couple of exceptions for highly news-driven content, which does make sense (for me) on a daily basis.
"When it comes to Newsletter success, consistency, and by that I mean daily, is everything."
My favorite newsletter so far was Ruby Weekly, which I read every week for several years, and I can say I wouldn't have been interested in it for daily. So I disagree that "daily is everything".
Was? :-D Haha, but yes, I think your opinion is the most common one amongst readers. To be fair, Ruby has stablized/plateaued to such a point that even weekly is pushing it in terms of quality sometimes. There are ways to approach daily newsletters in quiet niches that can work, but it always helps if it's a fast moving space (so "tech news" is ideal for daily, say).
I don't use Ruby much anymore, and my regular inbox is cluttered. Just signed up for JavaScript, React, Node, and Golang weekly in my hey.com account :)
* https://briefingday.com/