I heard a really interesting little show on the radio tonight, about the man who explained 'bands of nothing.' "Astronomer Daniel Kirkwood... is best known for explaining gaps in the asteroid belt and the rings of Saturn — zones that are clear of the normal debris." http://stardate.org/radio/program/daniel-kirkwood. He taught himself algebra, and used his math background to analyze the work of others, rather than making his own observations. The segment is only 5 minutes; give it a listen.
This reminded me of the how much progress I used to make when I did genealogy research, by looking over the documents I had gotten long ago, in light of facts I more recently uncovered. All of a sudden, I made new discoveries in those old docs. So that has become part of my regular research routine.
And perhaps all of these thoughts were triggered by the BASH bug which I keep hearing about on the news in very vague terms, and in quite specific discussion in IRC and mail lists. Old, stable code can yield new, interesting bugs! Maybe even dangerous vulnerabilities. So it's always worth raking over old ground, to see what comes to the surface.