I'd go further than that. I've come across a few programmers who had _only_ built new systems, or maintained systems they had built. You could cajole them about coding standards, documentation, unit tests, clear naming until you were blue in the face. It is pointless.

So you force them to maintain someone else's code base. Be prepared about the rants about how bad code base is, whinging about having to learn all the unfamiliar libraries, the total lack of comments, yada yada. But somehow the connection between how that programmer worked and how they worked is never made.

Then 6 months later, after a some of the intimate knowledge of their own code they were using to make maintain it tractable is gone, you move them back. Then, finally, it hits home. They improve steadily thereafter.

That was also when I learned you could deadlock AIX 3.2.5's NFS filesystem using mmap. (I was also working as one of the dept's sysadmins, so putting 2 and 2 together was easy.)