Yes. I would certainly stop short, though, of saying we don't have to worry about it until we know where we're going. One has to go a bit further than that. But you can also do it too early.
The classic case in point is the first Gulf War, when the U.S. put down very clearly, “We're not going to Baghdad. We're not going any further than this,” which at the time made eminent sense. And the military leadership loved it because it gave them a clear exit strategy. They knew exactly what to achieve, and at the end of that everybody could come home.
I think history has shown, though, that a more far-reaching look at this to consider changing the exit strategy might have actually saved us a lot of grief later on. So just because you have an exit strategy doesn't mean it's right. It makes it easy from the point of view of management of the campaign, but it needs to be revisited in terms of whether you're achieving your political objectives.