Ideally you can do that, but even the most well designed software ends up needing a larger refactor/reorganization that will touch a large portion of the code base.

My boss likes to say “you aren’t qualified to design something until you have built it once” which I do feel rings true. This inevitably leads to at least one major redesign for a significant codebase.

I think the first I used was Fedora Core 5, but the first I installed myself was Fedora Core 6.