Have to say I am pretty fond of systems science, particularly software engineering.

Programs are these formal structures. They do not rust or anything like that. But they still age in a way that all complex systems age.

One such consequence of this is that systems with a hardy design can last pretty much forever. There is a lot of "brown field" and a bunch of time is spent rebuilding especially important systems out of stronger logic.

But two areas that software seems to change, even in such bullet proof systems, is security problems and new hardware. Interfacing can mitigate upkeep costs from hardware growth. But security issues tend to cause rewrites. What fixes security upkeep requirements are small edge cases of mathematical purity. But I think most systems can never be so clean.