I've seen this kind of senior maintenance developer being allowed to flourish only once in my career. In my opinion, the key was project scope. It was complex e

I've seen this kind of senior maintenance developer being allowed to flourish only once in my career. In my opinion, the key was project scope. It was complex enough and had been in production long enough so that this maintenance wizard always had a wide range if issues to choose from. He got the reputation of knowing the whole complicated mess by heart, and being able to resolve the problems nobody else could. As a result, the management did not dare move him to new feature development, he got to work on what he liked, did it good, and thus cemented his position more and more. If the project had been any less of a mess (lucrative, highly lucrative mess), somebody in management would have insisted on "not wasting the talent" and moved him to churning out new features. Because features are always more important, unless the bugs become perfectly capable of sinking the whole project.