Mostly what I've done is maintenance mode, that's where if you try to touch something it is often very complicated in secondary effects and fixes, and requires

Mostly what I've done is maintenance mode, that's where if you try to touch something it is often very complicated in secondary effects and fixes, and requires lots of tests. And additions of functionality which are bolt-on will come with 10 years of accumulated requirements around the shape of any new code and the tests.