I can't speak for other articles, but my primer usually makes HN maybe once a year, unless I happen to write a new section and get lucky enough on upvotes when

I can't speak for other articles, but my primer usually makes HN maybe once a year, unless I happen to write a new section and get lucky enough on upvotes when I post a link to it myself. My normal pace of writing new sections is "maybe once every half year", this time I was requested to write about rotation minimising frames less than a month after the previous update, so if you remember seeing this same primer last month: you did indeed, although it was on a completely topic (namely, curve fitting).