Frequently. Whenever I run into something that makes little sense to me, I go back and look at the commit messages, the related bugs, the evolution of the code,

Frequently. Whenever I run into something that makes little sense to me, I go back and look at the commit messages, the related bugs, the evolution of the code, and who wrote it. It's called software archeology. It's not important if you keep exactly the same people working on the same project and they have perfect memory. But if you, say, move people between different teams, or lose people, or hire people, it's a gold mine.