I was having this dilemma on my walk home. I try to write good idiomatic Django code, and know how to make it efficient in the ways described in Two Scoops (a book about Django best practices). I have inherited an app, parts of which are exactly the opposite of Django best practices (thin models fat controllers being the most obvious one - the application's documentation says that's the philosophy , while Django encourages, and works better the opposite way).
So do I spend more time refactoring and bringing this application to a decent state, or do I just keep on hacking more crap on to it? No one except for me seems to give a shit as long as it seems to be working.