Long story short: You don't. After the delete window, you don't get to decide whether your posts stay up. You can email PG with a request, and you might be able to get certain posts deleted if you have a compelling reason, but I don't think entire posting histories are ever deleted for any reason besides spam. See also: <a href="http://news.ycombinator.com/item?id=3010641" rel="nofollow">http://news.ycombinator.com/item?id=3010641</a>
You don't.<p>We have your infos. FOREVER~.<p>Which we shall use as blackmail if you ever decide to do anything funny.<p>Like leave.<p>We are watching you.