The Best Time of Day to Learn a New Language
I came across the following article and thought I should share it with you. It's a rather lengthy article, yet interesting: https://qz.com/1215361/the-best-time-of-day-to-learn-a-new-language-according-duolingo-data/
I think you hit the nail on the head. These statistics are useful if you use them to reflect on how your learning. Once you start looking at what works and what doesn't it doesn't take much to get a little more out of each session.
I'd also like to see the age statistics. I imagine college students have the wildest variation on time (due to their class schedules).