The subscription model is a bit annoying, though, I'd prefer to spend a bit more to get lifetime access to sets of tutorials so that you can come back to it at any time in the future. The future upsell would be new tutorials sold to existing users. And it'd be nice to be able to buy it sliced either by language or by target. Most likely someone is learning Python so then they want to buy the Python set of courses, then they come back later and they're learning Go so they buy the Go set of courses, etc.