I think it is necessary in some cases to work extraordinarily hard, or perhaps even over a long period of time. But that in itself shouldn't really be a criteria for anything, IMHO, b/c it can lead to tunnel vision. At the very least, I keep seeing this mistake in my own approach to things.

Another thing I've noticed is that it also matters how much I like whatever it is I'm working on. If I like it a lot, I will naturally remember thing about it well, have better insight, and learn more about it. However, I may also be less productive because of this, i.e. going off on tangents.