I finished writing the second lesson this evening. I will spend a day or so polishing it before I release it.
I have built the game up to lesson 4 but planned well beyond that. And have started working on gathering screenshots and writing up a draft for lesson 3.
So what I will do is release lesson 2 very soon, lesson 3 likely next week.
It's taken me around 30 hours to complete lesson 2 (including creating the assets and building the game in a way that will suit the lessons) though.
Depending on the size of each lesson and how detailed I go into various aspects of game development, the course may take quite a few months to complete in full.
But I will attempt to make a big push to get the earlier lessons out asap. That way, we can get beyond the basics and move into the more meatier aspects of creating a platformer sooner rather than later.