If my kid is 18 and living at home, I have some say in the life. If they want 0 say, they can find their own way. Obviously, I don't give a rat's ass that my 18 year old games becasue as long as they have a healthy lifestyle, I'm glad they're enjoying themselves but if they're starting to become a hermit and losing friends, not working, not taking care of their health, etc, then they're going to have some pressure from me.
You don't get to live off the teet and also not listen at all.