I had a plan, that I would keep on practising those eight bars from Hava Nagila, over and over, until I had them just so, and could play them quickly, slowly, heavily, lightly, wtf. In the event, I never got that far, though I did spend several hours (altogether) with it. During that time, the improvement in the way my hands were working seemed tangible: I really was playing two handed, rather smoothly. But now I've moved on, even though I hadn't reached any sort of perfection with those eight bars.
I know that in language learning we'd never seek "perfection", there's no such thing. And maybe music should be treated in the same way? The only purpose that these eight bars serve is to help me learn - it's only a baby version of a tune which, later, I will perhaps come back to and learn properly - maybe a year or two from now. So, essentially, perfection is not a goal yet. My methodology (for now) will be to work through the lessons in the software, practising with the given pieces, but moving on once I can play them more-or-less. Flawless playing is then something I can work on as I start to learn the tunes that I love - which is the underlying rationale for all of this.