One of the goals of education is to form habits: to make the best way to do something the automatic way to do it. It turns out that may be harder than we thought. New research indicates that the oft-quoted "21 days" rule is a myth; the real figure is on average in the mid-60s, with some things taking significantly longer.
I think this is bad news for anyone teaching good programming practices at the university level. We don't have students long enough for things like using debuggers or test-driven development to bed down as habits. What's worse, their next instructor probably won't mention them at all (since his or her course is supposed to focus on databases or compilers, how students work just isn't on the radar), so the reinforcement needed to make good practice automatic isn't there.