[JohnFen]

It's a judgement call. If you're maintaining software, it's true that every time you touch the code -- even to fix a bug -- you're taking a risk that you're introducing a new bug. Refactoring software is an even greater risk.

So, in general, the instinct is (and should be) to touch the code as little as possible. However, that's not always the right answer. The right answer is to do a risk/benefit calculation and choose the approach that is most likely to lead to an overall improvement.

Sometimes, that means change as little as possible to fix a bug. Sometimes, that means refactoring a major piece. It all depends.