It's a lovely technique and just shows how useful the knife tool is. The only problem I have is stopping :-) I get caught up in putting detail in that I tend to go overboard!
How do you figure out when to stop?
This is where I hoped experienced users like yourself would go a bit overboard. There's lots of room to add details on details at this stage. So on one hand I want to say "take it as far as you can!"
Practically though I try to gauge what level of detail would be visible in my final render.