One or two links to an old post would not deteriorate the quality or freshness of content. In fact a lot of times one might be interested to get broader idea of the author stream of thoughts, for the ones not interested thye just have to blind to hyperlinks.

May be it would become restructured content if there are too many outward references like the... "Undergraduate" post. But even that when you look into this post the hyperlinks are for keywords like "essays", "hacker", "computer science", what you "love", hack a "blub" on windows ..