Unlike some of the time-travel movies I love, like 'Primer' or '12 Monkeys,' 'Looper' is not about time travel. It's about this situation that time travel creates and the people dealing with that situation. So narratively, the big challenge was to have time travel get out of the way.
I didn't do it because of the underlying greed that's prevailing, but it is about greed, doing the right thing at the right time using your clout when you have it and what for and what reason.