My newsletter "Le Courrier du hacker", is weekly digest of Free and Open Source Software news in the French-speaking community https://lecourrierduhacker.com/
I recently reached the 100th issue of my newsletter and I seized the opportunity to communicate as much as I could about the newsletter. I had good new arguments: with 100 issues, I was proven the newsletter was persistent. And we also reached 2k subscribers some weeks before the 100th issue so I had two major points to communicate about this newsletter.
Since then, almost 20% more signups happened, so I guess people were interested in joining a persistent newsletter of almost 2k subscribers already.