That swing goes both ways here - you've got people who do a lot of postwork, and you have people who don't. As far as "how far is too far" - it depends on the final result you want to achieve. The key is in learning control over whatever tools you use - being able to previsualize and then create towards that previsualization. (Personally, I'm not much of a fan of "dumb-luck" works - I mean, give an infinite number of monkeys and infinite number of typewriters - one of them will write Hamlet.