I can't remember how old I was when it happened.
My dad got pulled over for not wearing a seatbelt. Actually, he got pulled over for tossing a cigarette out the window. He didn't even realize what he'd done. The officer let him off with a warning because he appeared to feel bad about it. Eventually, he started wearing a seatbelt and stopped smoking. It took a real health scare, in his 60s.
My dad isn't stupid.
He's an engineer.
Even today, he avoids large crowds. He wears an n95 respirator when he goes to buy groceries. He knows how to make steel. He knows how to hack computer games. He can code. He can draw. He still doesn't recycle. Not even glass or cardboard. It doesn't enter his head. It doesn't matter how many times I bring it up. He'll say he should. Then he doesn't.
So, if you want to know how long it can take for an intelligent person to change their behavior, try 20 years. Even then, they're going to do some smart things and some dumb, selfish things.
I keep asking why.