My goal is to ensure that the company is in a position to carry on with as little disruption as possible. I've always given at least the (US standard) two week

My goal is to ensure that the company is in a position to carry on with as little disruption as possible. I've always given at least the (US standard) two weeks, and usually three, but much longer than that can be counterproductive because one can become entrenched in current projects instead of wrapping things up and transitioning them to others. Even when I've been at the same company for many years and have been involved in a lot of projects, this never took more than two weeks because throughout my tenure I do my best to document things, cross-train my co-workers, and ensure that others could take over for me if needed. That last two weeks is usually just a matter of making sure that all my documentation is up-to-date and that people remember what I've taught them.