@sgf Yeah I think the fancy name is 'Transformational Architecture' or less fancy 'code jenga'; changing a running app and making it better while keeping it running I think only really comes from experience. The irony is that the more able you are to manage that sort of thing the less likely you'll be in a role which allows it.
@scottgal I've seen people successfully keep doing such stuff, really well, at the expense of "career advancement", but yeah.
On the other hand, you get more opportunities to teach/lead others to do so. Although that's not to everyone's taste I guess.