Yeah - there are probably exceptions ;-) However what I've seen happen on multiple occasions is somebody merrily driving along churning out code then suddenly

Yeah - there are probably exceptions ;-) However what I've seen happen on multiple occasions is somebody merrily driving along churning out code then suddenly hitting the "ohhh - duplication is bad" wall and halting as they feel their way around the duplication and abstract they may need (or may not - since they've not written the code yet). Duplication is not a mortal sin. Having it sit there for a few hours while you work out the meat of the problem isn't going to kill any kittens. And often the easiest way to fully grok the abstraction that you need is to make the duplication really, really obvious.