This is kind of one of those issues that can really cut both ways. I don't think it's the best attitude to say, "it's been working for years, so it's fine"; the

This is kind of one of those issues that can really cut both ways. I don't think it's the best attitude to say, "it's been working for years, so it's fine"; there could be subtle bugs, and areas rarely exercised. Still it often holds true. We all remember times we've meddled with something and messed it up. It seems that some of the low level code has been really heavily used in many different ways, and seems to just work. Especially if it's not safety/security critical (and maybe even if it is), it could be a poor use of resources trying to fix something that isn't broken.