Related to my note the other day on the ideal length of various pieces of art, a post on Medium reveals that the optimal post length there (if your criteria is what length Medium post entices readers to spend the most time on it) is 7 minutes.
The post revealing this was, appropriately, 7 minutes in reading time.
[Somewhat related: I don't ever find myself glancing at the estimated time to read figure on any of Medium's posts. I'm not sure if it's because I am time insensitive or that my sense of time is so subjective that I just ignore the numbers, or if it's something else. Do others find reading time estimates for content useful?]