Zero days is enough. Obviously, that's not enough time for them to replace you, and probably two weeks isn't enough time either. But that is not your responsibility, it is theirs. So, I'd say give 2 weeks because that is customary and it will preserve your relationships and professional reputation. It doesn't matter how the company manages in your absence. If it is very damaging for them, it only means they should have done better contingency planning. When I was younger, I used to worry a lot about how my colleagues and my boss would handle the disruption. Now that I've been around, I learned I was wrong about my relationship to the company. It's not about being jaded but understanding where your obligation begins and ends. I live in a big corporate context, and things are a bit different in small companies. But not that different. My wife and I own a small company. And when a key employee leaves, it significantly messes up the whole company. But we are the owners. We know it is on us, not the employee. So on the one hand we don't resent employees doing what they have to do for their own lives, while on the other we do what we have to do to protect the company from the risk a key employee leaves. So, 2 weeks. But that's for you and your reputation. Not for the company or your former colleagues. You have no obligation there.
My younger staff do not even give two weeks' notice. They just stop coming in and ghost you. And when HR makes you call them to confirm NO ONE ever answers
